Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
NITRIC OXIDE RELEASING PRODRUGS OF THERAPEUTIC AGENTS
CONTAINING AT LEAST ONE CARBOXYLIC ACID GROUP
Field of the Invention
The present invention relates to nitric oxide releasing prodrugs of known
drugs or therapeutic agents which are represented herein as compounds of
formula (I) wherein the drugs or therapeutic agents contain at least one
carboxylic acid group. The invention also relates to processes for the
preparation of the nitric oxide releasing prodrugs (the compounds of formula
(I)), pharmaceutical compositions containing them and methods of using the
prodrugs.
Background of the Invention:
Many drugs (therapeutic agents) have undesirable properties, for instance,
low oral drug absorption, toxicity, poor patient compliance etc., that may
become pharmacological, pharmaceutical, or pharmacokinetic barriers in
clinical drug application. Among the various approaches to minimize the
undesirable drug properties, while retaining the desirable therapeutic
activity, the chemical approach using drug derivatisation offers perhaps the
highest flexibility and has been demonstrated as an important means of
improving drug efficacy (Hyo-Kyung Han and Gordon L. Amidon AAPS
PharmSci. 2000;2 (1)).
The conventional approach that is adopted to minimize the toxic side effects
associated with the therapeutic agents has been to derivatise one or more
functional groups present in the drug molecule. The derivatives are then
assessed for their therapeutic efficacy as well as toxicity. The carboxylic
acid group is often present as an active functional group for derivatisation
in
several therapeutic agents. Non-steroidal anti-inflammatory drugs (NSAIDs)
represent one of the best class of drugs
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containing a carboxylic acid group as an active functional group. NSAIDs
are also the most commonly used drugs to relieve pain, symptoms of
arthritis and soft tissue inflammation. Most patients with rheumatoid
arthritis receive NSAIDs as a first-line treatment which is continued for
prolonged periods. Although, NSAIDs provide anti-inflammatory and
analgesic effects, they also have adverse effects on the upper
gastrointestinal (GI) tract. The occurrence of GI toxicity appears to be
strictly correlated to the mechanism of action of these drugs, namely the
inhibition of the enzyme cyclooxygenase. In fact, inhibition of platelet
cyclooxygenase, which causes prolonged bleeding time, and inhibition of
cyclooxygenase in gastrointestinal mucosa, which results in a decreased
synthesis of cytoprotective gastric prostaglandins, represent the major
cause of serious gastrointestinal toxicity (Symposium on "New Anti-
inflammatory agents: NO-NSAIDs and COX-2 inhibitors" part of the 11th
international conference on "Advances in prostaglandin and leukotrine
research: Basic science and new clinical applications" held in Florence
(Italy), June 4-8, 2000). This problem has been solved by derivatisation of
carboxylic acid group of NSAIDs into its ester and amide derivatives.
Another common approach to minimize adverse effects of the known
drugs or therapeutic agents consists of attaching a carrier group to the
therapeutic agents to alter their physicochemical properties and then
subsequent enzymatic or non-enzymatic cleavage to release the active
drug molecule (therapeutic agent). The therapeutic agent is linked through
a covalent linkage to specialized non-toxic protective groups or carriers or
promoieties in a transient manner to alter or eliminate undesirable
properties associated with the parent drug to produce a carrier-linked
prod rug
Indeed, a more recent strategy for devising a gastric-sparing NSAID
involves chemically coupling a nitric oxide (NO) releasing moiety to the
=
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parent NSAID. The approach and possibility of combining a few classes of
drugs bearing different functional groups susceptible of derivatisation with
NO-donating moieties has been described by Menlo BoIla et al., in Curr.
Topics Med. Chem. 2005; 5: 707-720.
Nitric oxide is one of the most important mediators of mucosal defense,
influencing factors such as mucus secretion, mucosal blood flow, ulcer
repair and the activity of a variety of mucosal immunocytes (Med
Inflammation, 1995;4: 397-405). It has been reported to play a critical role
in maintaining the integrity of the gastroduodenal mucosa and exerts many
of the same effects as endogenous prostaglandins (Drugs-Fut 2001; 26(5);
485). Several mechanisms are considered to underlie its protective effect
in the stomach including vasodilation of local mucosal blood vessels,
inhibition of leukocyte adhesion and inhibition of caspase enzyme activity.
The inactivation of caspase(s) appears to be an important factor in the GI
tolerance of nitric oxide releasing NSAIDs (NO-NSAIDs) (J.E. Keeble and
P.K. Moore, British Journal of Pharmacology, 2002; 137: 295-310). Nitric
oxide can thus be used to devise a gastric-sparing NSAID. Compounds
that release nitric oxide in small amounts over a prolonged period of time
may be very useful for the prevention of gastrointestinal injury associated
with shock and with the use of drugs that have ulcerogenic effects
(Muscara M.N.; Wallace J.L. American Journal of Physiology,
Gastrointestinal and liver physiology, 1999; 39: G1313-1316).
In recent years, several NO-releasing non-steroidal anti-inflammatory
drugs (NO-NSAIDs) have been synthesized by an ester linkage formed
through coupling of a NO-releasing chemical spacer group to the
carboxylic acid moiety of a conventional NSAID. The use of various
aliphatic, aromatic or heterocyclic chemical spacers makes it possible to
alter various physicochemical properties and kinetics of nitric oxide release
(Berguad et al., Ann. N. Y. Acad. Sci. 1962: 360-371 (2002)). The first NO-
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aspirin drug NCX 4016, which was synthesized relatively recently, consists
of an aspirin molecule linked by an ester bond to a molecular spacer,
which in turn, is linked to a nitro-oxy ester group (Dig Liver Dis 2003; 35
' (suppl. 2):9-19). A number of NO-NSAID hybrid compounds, namely NO-
naproxen (Naproxcinod), NO-flurbiprofen (HCT 1026), NO-ibuprofen, NO-
, diclofenac and NO-indomethacin have been disclosed in the patent
numbers EP 722434B1, US 6613784B1 and US 7220749k, respectively.
European Patent EP 722434B1 discloses nitrate esters of the derivatives
=
of propionic acid, 1-(p-chlorobenzoy0-5-methoxy-2-methyl-3-indolylacetic
acid and 5-benzoy1-1,2-dihydro-3H-pyrrolo[1 ,2-a]pyrrole-1-carboxylic acid
having anti-inflammatory and/or analgesic activity. U.S. Patent No.
6613784B1 discloses nitro derivatives of NSAIDs, for instance,
flurbiprofen, indomethacin, aspirin, naproxen and diclofenac. U.S. Patent
No. 722074962 discloses novel nitrosated and/or nitrosylated derivatives
of COX-2 selective inhibitors, U. S. Patent Application Publication no.
20080293781A1 describes 0-acyl salicylic acid derivatives bearing a NO
donor moiety. US Patent No. 7199154 B2 discloses nitrosated or
nitrosylated prodrugs for COX-2 selective inhibitors that are useful for
treating COX-2 mediated diseases or conditions and which can be
administered alone or in combination with low-dose aspirin. The
compounds are effective in treating chronic COX-2 mediated diseases or
conditions, reducing the risk of thrombotic cardiovascular events and
possibly renal side effects and at the same time reduce the risk of Cl
ulceration and bleeding. US Patent Application Publication no.
20060058363 Al discloses nitric-oxide releasing prodrugs of celebrex and
valdecoxib which are useful in the treatment of COX-2 mediated diseases.
The compounds may be used as a combination therapy with low-dose
aspirin to treat COX-2 mediated diseases or conditions while
simultaneously reducing the risk of thrombotic cardiovascular events.
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Nitric oxide (NO) also plays an important role in numerous other
physiological and pathophysiological conditions, e.g. blood pressure
regulation, inflammation, infection and the onset and progression of
malignant and cardiovascular diseases (Lirk, P., Hoffmann, G., and
Rieder, J. Cum Drug Targets Inflamm, Allergy 2002; 1:89-108). Though
delivery of supplementary NO in the form of NO-donor drugs has long
been an attractive therapeutic strategy (Ian L Megson, David J Webb,
Expert Opin. Investing. Drugs, 2002; 11(5): 587-601), in recent years, with
the advent of NO-NSAID approach and because of the beneficial
biochemical and pharmacological properties of nitric oxide, the strategy of
linking NO-releasing moieties has been extended to a wide array of
therapeutic agents selected from cardiovascular drugs, for instance,
Angiotensin converting enzyme (ACE) inhibitors, calcium antagonists and
beta-blockers, antitumor agents, antihistamines, glucocorticoids, etc. The
aim of this strategy is to synthesize prodrugs that retain the
pharmacological activity of the parent drug molecule coupled with the
benefits of the biological actions of NO in reducing the adverse effects of
the parent drug molecule.
US Patent Nos. 6,610,676 and 7,524,836B2 disclose nitrate esters and
nitrooxy derivatives of steroidal compounds having anti-inflammatory,
immunodepressive and angiostatic activity or gastrointestinal activity.
PCT Application Publication W02007099548A1 discloses 11p-
hydroxyandrosta-4-3-one compounds which possess useful anti-
inflammatory activity whilst having insignificant or no noteworthy side-
effects ' at efficacious doses. PCT Application
Publication
W02008095809A1 discloses derivatives of known corticosteroids,
containing a NO-releasing moiety which are useful in the treatment of
illnesses wherein the known corticosteroid, parent or precursor steroid, is
generally applied, with increased benefit in terms of pharmacological
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profile and fewer or milder side effects than those of the parent
corticosteroids.
The NO-releasing derivatives and prodrugs of various therapeutic agents
known in the art are in different phases of clinical development and there
are reports suggesting that a few of them have been suspended because
of some problems (see press reports on napr9xcinod and NCX4016 at
www.nicox.com). Therefore, there is a clear unmet medical need for new,
alternative and better NO-releasing nitrate ester prodrug compounds .
which can exhibit improved therapeutic properties.
One such class of compounds can be represented by the following generic '
= or Markush structure (IA):
0
=
Xz
NO2
Dx 0 0
(IA)
Wherein,
Dx represents a part of a drug or therapeutic agent containing at least one
carboxylic acid group which forms a bio-cleavable ester bond with the
specified linker and such drug or therapeutic agent is selected from the
group consisting of non-steroidal anti-inflammatory, analgesic and
antipyretic drugs such as aspirin, diclofenac, naproxen and the like, COX-2
inhibitors, angiotensin-II receptor blockers such as sartans (i.e., losartan,
valsatan, candesartan, telmisartan, eprosartan and olmesartan), ACE
inhibitors such as captopril, enalapril and the like, beta (13)- blockers such
as timolol, atenolol and the like, HMG-CoA reductase inhibitors
(cholesterol-reducing agents) such as statins (i.e., fluvastatin, pravastatin,
cerivastatin, atorvastatin and rosuvastatin), antiulcerative agents such as
misoprostol acid and so on among others;
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XZ independently represents at each occurrence a linear or branched
alkylene Cl-C20 preferably alkylene C1-C10, yet preferably alkylene C1-C6,
yet preferably alkylene C2-C10, substituted alkylene C1-C20, substituted
alkylene C1-C10, cycloalkylene C3-C7, cycloalkylene C5-C7, optionally
substituted cycloalkylene C3-C7 or C5-C7, or [C(Ra)(Rb)],õ
Wherein,
m = 1-20, preferably 1-10, yet preferably 1-6 01 2-10 or 2-5;
Ra and Rb at each occurrence are independently a hydrogen, substituted
or unsubstituted straight or branched alkyl C1-C20, preferably alkyl CI-Cm
or yet preferably alkyl C1-C6 or
Ra and Rb taken together with the carbon atom to which they are attached
form a cycloalkyl group, and so on among others;
The above Markush formula (IA) is deduced from the following 20 relevant
patent applications.
1. W02007054451 (Nicox S.A., Fr.).
2. CN101053662 (Jiangsu Wuzhong Suyao Drugs Development Co.,
Ltd., Peop. Rep. China).
3. W02005070868 (Merck Frosst Canada & Co., Can.).
4. W02005030224 (Nicox S.A., Fr.).
5. W02005011646; Family: AU2004260830 (Nicox S.A., Fr.).
6. W02004035042, Family: AU2003269774 (Astrazeneca UK Limited,
UK).
7. W02004004648, Family: CA2491127 (Nitromed, Inc., USA).
8. W02003094923, Family: AU2003236636 (Scaramuzzino, Giovanni),
W02003084550, Family: AU2003224002 (Nicox S.A., Fr.).
9. EP1219306, Family: AU2002219225 (Nicox S.A., Fr.).
10.W09821193, Family: CA2272063 (Nicox S.A., Fr.; Del Soldato, Piero).
11.W09809948, Family: EP931065 (Nicox S.A., Fr.).
12.W09716405, Family: EP871606 (Nicox S.A., Fr.).
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13.W09530641, Family: EP759899 (Nicox Ltd., Ire.).
14.W02007088123, Family: AU2007211508 (Nicox S.A., Fr.).
15.CN1966484 (Beijing Meibeita Pharmaceutical Research Co., Ltd.,
Peop. Rep. China).
16.W02004020384, Family: EP1532098 (Nicox S.A., Fr.).
17.W02001010814, Family: EP1200386 (Nicox S.A., Fr.).
18.W02009000592, Family: EP2164484 (Nicox S.A., Fr.).
19.W02004105754, Family: US7166638 (Nicox S. A., Fr.).
20.W09858910, Family: EP989972 (Nicox S.A., Fr.).
We now report a small set of compounds of formula (I) which possesses
surprising and unexpected properties when compared with compounds of
formula (IA).
0 H Ry
)c Dx 0Xo.-' NO2
(I)
Wherein,
Dx is a part of a drug/therapeutic agent containing at least one carboxylic
acid group [i.e., DxCO21-1] which is covalently bonded to the specified linker
"C(H)(Ry)" via a bio-cleavable ester linkage;
Ry is an alkyl Ci_Cs or cycloalkyl C3_C7; preferably alkyl C1.C4; yet
preferably alkyl C1.C2; yet most preferably Ry is methyl (i.e., CH3);
0NO2 (a nitrooxy) group_ is covalently bonded to the other side of the
linker;
and all its geometrical and stereoisomeric forms and pharmaceutically
acceptable salts thereof.
The compounds of the present invention represented by formula (I) are
generically covered within the scope of some of the patents or patent
applications listed above.
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Obviously, the Markush formula (IA), with so many variables, would
encompass several thousand or even millions of possible compounds
including the compounds of formula (I) of this invention. However, none of
the above mentioned prior art documents specifically disclosed or claimed
any of the possible compounds of this invention that are represented
specifically by the formula (I).
A characteristic and unique structural feature of the specific set of
compounds of formula (I) of the invention (i.e., representing a species)
when compared to those of the compounds of formula IA (i.e.,
representing a genus) is the presence of a unique "acyl-acetal" type
linkage represented by "-C(=0)-0-C(H)(Ry)-0-" group, which is a "hybrid"
form of an ester and an acetal group. This characteristic and unique
structural feature possibly imparts hitherto undisclosed properties to the
compounds containing this "acyl-acetal" type linkage which are essentially
the compounds of this invention specifically represented by the formula (I).
Some of the characteristic properties exhibited by these unique set of
compounds include:
1. The compounds of formula (I) are the only kind of nitric oxide releasing
ester prodrugs of carboxyl-containing drugs that encompass the
unique "acyl-acetal" type structural feature.
2. Upon incubation in simulated gastric and/or intestinal fluid/s, the
compounds of formula (I) readily released significant amounts of
parent drugs (including aspirin!). It is well known to the people skilled
in the art that it has been a very difficult task to design a true ester
prodrug of aspirin due to the presence of a very labile acetyl group
which undergoes preferential hydrolysis by plasma esterases.
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Consequently, a vast majority of ester prodrugs of aspirin turn out be
prodrugs of salicylic acid. However, in case of aspirin, the promising
NO-aspirin prodrug 1-DI-RI (i.e. Dx = D1 = aspirin; Ry = R1 = CH3) of
the present invention was seen to act as a true prodrug of aspirin,
when tested for its capability to release aspirin in Simulated Gastric
Fluid (SGF) (Figure 8) and Simulated Intestinal Fluid (SIF) (Figure 9).
The prodrug 1-DI-RI was evaluated at a concentration of either 100
piN1 or 1 mM in SGF (aspirin was co-evaluated as a positive control
under the same experimental conditions, at equimolar doses) and has
shown dose dependent decrease/increase in the amount of aspirin
released. In SIF also, the prodrug I-D1-R1 released significant amount
of aspirin at 1 mM concentration. However, although the aspirin
release increased in a dose-dependent manner, it was significantly
less than that of aspirin standard at equimolar doses. In SIF, with its
pH in the range of -6-7, a certain percentage of the prodrug
preferentially underwent de-acetylation to give salicylic acid
intermediate which further degraded to salicylic acid.
Interestingly, the behaviour of NO-aspirin (i.e. Dx = D1 = aspirin)
prodrugs of formula (I) was seen to be significantly different from the
analogous compounds of formula (IA) [(i.e., with the same molecular
formula and molecular weight but with different structural features; i.e.,
structures I-D1-R1 and II-D1-X2, respectively). When these two
compounds were incubated simultaneously in SGF, it was observed
that only the compound of formula (I), i.e., I-D1-R1, of the present
invention, released quantitative amounts of the parent drug aspirin
whereas the compound of formula (IA) i.e., II-D1-X2, quickly
decomposed into an unknown metabolite, without releasing even
traces of aspirin. Additionally, another analogous NO-aspirin
compound NCX-4016 of formula (IA) that had reached phase II clinical
trials (structure shown below) remained intact (no release of parent
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drug, aspirin) when incubated in SGF under identical conditions (Table
1).
H3c)Lo 0 cH, H3C)N.0 H3C-j10 o
0,
40, 02 0 NO2
1-D1-R1 II-D1-X2 [Xz X2 = CH2CH2] II-D1-X1 [Xz X1 = in-
C6H4CH2] ,
MF: C111-111N07 MF: CI 11-111N07 MF: CI6H13N07
MW: 269.21 MW: 269.21 MW: 331.28
Table 1: Stability study of NO-aspirin prodrugs in SGF ____
Time I-Dl-R1 II-D1-X2 II-D1-X1 [NCX-4016]
Point (Ry = R1 = CH3) [Xz = X2 = CH2CH2] [Xz = X1 = m-C6H4CH2]'
(min) % of Prodrug % of Aspirin % of Prodrug A of Aspirin % of Prodrug % of
Aspirin
remaining Released remaining Released remaining
Released
(I-tM) (1-1M) _ (IAM) _4tM) _ (IAA) (1N)
0 91 0 The prodrug Aspirin 100.00 Aspirin
5 82 18 underwent release was 100.00
release was
56 44 quick not observed 100.00 not
observed
30 3 97 decomposition 100.00
60 0 - 100 into an 100.00
120 0 100 unknown 100.00
metabolite
t112 <15 min -1.5 min
In case of naproxen series also, the behaviour of NO-naproxen (i.e.
10 Dx = D2 = naproxen) prodrugs of formula (I) was seen to be
significantly different from the analogous compounds of formula (IA)
(i.e., with the same molecular formula and molecular weight but with
different structural features; See structures I-02-R1 and II-D2-X2,
shown below); when incubated simultaneously in SGF, it was
observed that only the compound of formula (I) of the present
invention i.e., I-D2-R1 released quantitative amounts of the parent
drug, naproxen whereas the compound of formula (IA) i.e., II-D2-X2
remained intact (no release of parent drug naproxen) under identical
conditions (Table 2).
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CH3 CH
, 3
õ
0
NO2 .---,-,/'y, -oNo2
Me0 Me0
,-,-,_,,,,-I o CH3 ,--,,,,,,,..õ>.,-I 0
I-D2-R1 II-D2-X2 [X2 = (CH2)0
Chemical Formula: C16F117N06 Chemical Formula: C161-117N06
Molecular Weight: 319.31 Molecular Weight: 319.31
Table 2. Stability of prodrugs I-02-R1 and 11-D2-X2 in SGF
Time I-D2-R1 (Ry = R1 = CH3) II-D2-X2 Vz = X2 = (C
H2)2]
(mins) I-02-R1 Naproxen II-02-X2 Naproxen
Remaining (%) Released (%) Remaining Released (%)
(%)
0 100.00 0.00 100.00 0.00
84.68 15.32 99.68 0.32 ,
74.58 25.42 99.79 0.21
64.58 35.42 99.68 0.32
30 32.79 67.21 99.75 0.25
60 0.00 100.00 99.67 0.33
120 0.00 100.00 99.39 0.61 .
180 0.00 100.00 99.19 0.81
tin 20-25 min NA
5
Even the higher homologue pairs of naproxen prodrugs of formula (I) and
formula (IA) i.e., I-D2-R2 vs II-02-X3 and I-02-R3 vs 11-02-X4 behaved in
a similar fashion, when incubated simultaneously in SGF. Thus only
compounds of formula (1) i.e., I-D2-R2 and I-D2-R3 released naproxen
10 (Tables 3 and 4, respectively).
,
CH3 CH3
7.:
I *
Me0 0 CH3 Me0 0
I-D2-R2 II-D2-X3 [X3 = (CH2)3]
Chemical Formula: C17H19N06 Chemical Formula: C12H19N06
Molecular Weight: 333.34 Molecular Weight: 333.34
Table 3. Stability of prodrugs I-02-R2 and II-D2IX3 in SGF
1 Time I-D2-R2 (Ry = R2 =
CH3CH2) II-D2-X3 [Xz = X3 = (CH2)31]
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(mins) I-D2-R2 Naproxen II-D2-X3 Naproxen
Released (%) Remaining Released (%)
Remaining (lo) (y.)
0 100 0.00 100.00 0.00
94.33 5.67 100.00 0.00
90.43 9.57 100.00 0.00 _
74.27 25.73 100.00 0.00 =-,
30 62.15 37.85 100.00 0.00
60 51.01 48.99 100.00 0.00
120 39.08 60.92 100.00 0.00 -
180 6.77 93.23 100.00 0.00 ,
tin . '''l h NA
cH3 0H3 .
,-
NO2 NO2
0
't--ICH3 , .-' `-,
,--"=-k--,õ-,-71
Me0 Me0 0 .
I-D2-R3 II-132-X4 [X4 = (CH2)4]
Chemical Formula: C18F121N06 Chemical
Formula: C18H21N06
Molecular Weight: 347.36 Molecular Weight: 347.36
5
Table 4. Stability of prodrugs I-02-R3 and II-D2-X4 in SGF
Time I-D2-R3 (Ry = R3 = CH3CH2CH2) H-D2-X4 (Xz = X4 = (CH2 4]
(mins) I-D2-R3 Naproxen II-D2-X4 Naproxen
Released (YO) Remaining Released (%)Remaining (to)
(%)
0 100 0.00 100.00 0.00
5 96.35 3.65 100.00 0.00
10 93.61 6.39 100.00 0.00
15 83.21 16.79 100.00 0.00
30 82.73 17.27 100.00 0.00
60 75.48 24.52 100.00 0.00
120 57.55 42.45 100.00 0.00
180 39.00 61.00 100.00 0.00
=
tin ."' 2.5 h NA
A still higher homologue of naproxen prodrug of formula (I), i.e., l-D2-R4,
10 also released appreciable amounts of the parent drug naproxen when
incubated in SGF, as shown below (Table 5).
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CH3
0 O.,
Me0 CH3
1-132-R4
Chemical Formula: C19H23N06
Molecular Weight: 361.39
Table 5. Stability of prodrug I-D2-R4 in SGF
Time I-D2-R4 (Ry = R4 = CH3CH2CH2CI-12)
(mins) I-D2-R4 Naproxen
Released (%)
Remaining WO
0 100 0.00
5 97.74 2.26
10 96.18 3.82
15 87.41 12.59
30 90.53 9.47
60 88.87 11.13
120 79.97 20.03
180 71.04 28.96
t1/2 > 3 h
From the above data, it is obvious that the compounds (prodrugs of
naproxen) of formula (I) release decreasing amounts of parent drug
naproxen with increasing alkyl chain length of Ry (probably due to
solubility issues associated with increased hydrophobicity of longer alkyl
chains). Thus, the half-lives (tv2) of prodrugs of naproxen of formula (I)
follow the pattern: I-D2-R1 (t112 = 20-25 min) < I-D2-R2 (t112 = 1 h) < I-
D2-R3 (t112 = -- 2.5 h) < I-D2-R4 (tv2 = > 3 h).
Similarly, I-D3-R1, which is the nitric oxide releasing prodrug of
chlorambucil of formula (I) (i.e., Dx = D3 = chlorambucil; Ry = R1 = CH3)
also released its parent drug chlorambucil quantitatively when incubated in
SGF as shown below (See Table 6 and Figure 12).
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CI
o CH3
j<s=H NO2
0
I-D3-R1
Table 6. Stability of prodrug I-D3-R1 in SGF
Time 1-D3-R1 (Ry = R1 = CH3)
(mins) 1-D3-R1 Chlorambucil
Released (%)
Remaining (%)
0 - 92.12 7.88
20.49 79.51
10 13.84 86.16
15 8.59 91.41
30 0.00 100.00
60 0.00 100.00
120 0.00 100.00
180 0.00 100.00
t112 < 5 min
Interestingly, the chlorambucil prodrug I-D3-R1, which is the lowest
5 carbon
homologue among the chlorambucil prodrugs of formula (I),
decomposed in SGF to give 100% of the parent drug chlorambucil, with a
half-life of less than 5 minutes (Table 6).
3. The compounds of formula (I) exhibited nearly similar or superior oral
bioavailability and efficacy as compared to those of respective parent
drugs in rats (See Figures 1, 2, 3 and Table 7).
4. Although the compounds of formula (I) at equimolar doses exhibited
nearly similar or superior oral bioavailability and efficacy as compared
to those of their respective parent drugs, they did not cause any
significant drug-induced gastric lesions and/or bleeding. However,
their respective parent drugs at equimolar doses caused significant
drug-induced gastric lesions and/or bleeding (See Figures 5 and 6).
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5. The process for making the compounds of formula (I) differs
significantly when compared to the reported processes for making the
compounds of formula (IA).
For example, the most frequently used process for making the
compounds of formula (IA) involves the steps, as shown in the Chart
1A:
Step 1:
0 0
OH (C0CO2/DMF
)1
Dx DCM Dx \CI
Dx Dx-C(-=0)CI
Step 2:
,Xz CBr4, TPP, DCM Xz
701.
HO ."OH HO Br
HO-Xz-OH HO-Xz-Br
Step 3:
Xz AgNO3 Xz NO2
w HO tOt-
HO"- Br ACN
HO-Xz-Br HO-Xz-0NO2
Step 4:
0 0
,Xz NO _LTEL )-(.õ xz NO2
Dx CI HO '0"- DCM Dx 0 /Cr
HO-Xz-0NO2 (IA)
Chart 1A: The most usual process for the synthesis of compounds of formula
(IA)
Step 1: Conversion of the drug or therapeutic agent containing
carboxylic acid group (Dx-CO2H) to its active acid chloride Dx-C(=0)CI
by reacting with thionyl chloride or oxalyl chloride in presence of
catalytic amount of DMF;
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Step 2: Conversion of diol HO-Xz-OH for example 1,2-Ethanediol or
1,3-Propanediol or 1,4-Butanediol (wherein Xz is as defined above),
into its mono bromide derivative HO-Xz-Br, by known methods for
example by treating with carbon tetrabromide and triphenylphosphine
in a solvent such as DCM;
Step 3: Conversion of monobromide HO-Xz-Br from Step 3 into the
corresponding mononitrate HO-Xz-0NO2 by treating with silver nitrate
in acetonitrile;
Step 4: Reaction of acid chloride from Step 1 with the mononitrate
from Step 3 in the presence of a suitable base such as triethylamine in
a suitable solvent such as DCM to yield the compound of formula (IA).
In contrary, the process for making the compounds of formula -(1)
involves significantly different steps as shown in Schemes 1 and 2.
For clarity, a plausible mechanism for the formation of the compounds
of formula (I) is shown below:
Ry 0 H RY 0 RY
ZnCl2 AgNO3 ,..)c X
NO2
Dx Zrfe= 1.4171- DCM Dx 0 CI ACN Dx 0
CI mcr¨
Dx¨C(.0)CI Ry-CHO Dx¨Ry¨CI l-Dx¨Ry (I)
Wherein,
Dx = drug or part of the drug containing at least one carboxylic acid group;
Dx-C(0)Cl can be freshly prepared from Dx-CO2H by using a known method; and
Ry = Alkyl C1-C6.
Chart 1B. A Plausible mechanism for the formation of composition of the
compounds of formula (I)
It would be understood by a person skilled in the art that in the
compounds of formula (I), the "CO" group adjacent to Dx is derived
from the carboxyl group of the drug (i.e., Dx-CO2H) as shown in chart
1B.
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The above mentioned characteristic properties of the unique compounds
of the present invention represented specifically by the formula (I) [i.e.,
representing a specific species comprising the compounds of formula (I)]
are neither disclosed specifically in the prior art [i.e., representing the
whole genus comprising the compounds of formula (IA)] nor obvious to
those skilled in the art to which this invention relates. The unique
structural
features and characteristic properties of the compounds of formula (I)
therefore constitute or impart both "novelty and inventive features" to these
potentially useful compounds.
BRIEF DESCRIPTION OF DRAWINGS:
Figure 1. Oral absorption profile of aspirin and its prodrugs I-D1-R1 (i.e.,
P7097), I-D1-R2 (i.e., P7244) and I-D1-R3 (i.e., P7245) in SD Rats; A)
Line graph; B) Bar graph.
Figure 2. Oral Absorption profile of aspirin and its prodrug I-D1-R1 in
Wistar Rats; A) Line graph; B) Bar graph.
Figure 3. Oral absorption profile of naproxen and its prodrugs I-D2-R1
(i.e., P7133), I-D2-R2 (i.e., P7135), I-D2-R3 (i.e., P7134) and I-D2-R4 (i.e.,
P7132) in SD Rats; A) Line graph; B) Bar graph.
Figure 4. Plasma NOx (nitrate/nitrite) levels following oral administration of
prodrugs I-D1-R1 and I-D2-R1 in rats.
Figure 5. A) Images of rat stomachs showing gastric lesion and ulcer
induction/sparing following acute oral administration of aspirin (100 mg/kg)
and its promising prodrug 1-DI-RI (i.e., P7097 or NO-aspirin) at 298.85
mg/kg, which is a dose equimolar to 200 mg/kg of aspirin; B) Gastric lesion
& ulcer area (mm2) of rat stomachs after acute oral dosing of rats with
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aspirin (100 mg/kg) and its prodrug I-D1-R1 (298.85 mg/kg, which is a
dose equimolar to 200 mg/kg of aspirin).
Figure 6. A) Images of rat stomachs showing gastric lesion and ulcer
induction/sparing following acute oral administration of naproxen sodium
(109.52 mg/kg, which is equimolar to 100 mg/kg dose of naproxen) and its
promising prodrug I-D2-R1 (i.e., P7133 or NO-naproxen) at 138.67 mg/kg,
which is a dose equimolar to 100 mg/kg dose of naproxen in rats; B)
Gastric lesion area (mm2) of rat stomachs after acute oral dosing of rats
with naproxen sodium (138.67 mg/kg, which is a dose equimolar to 100
mg/kg dose of naproxen) and its prodrug I-D1-R1 (138.67 mg/kg, which is
a dose equimolar to 100 mg/kg of naproxen).
Figure 7. In vivo inhibition of TXB2 (i.e., indicated by the reduction in
serum
TXB2 levels) after oral dosing of rats with aspirin (30 mg/kg) and its
promising prodrug I-D1-R1 (i.e., P7097 or NO-aspirin, 44.82 mg/kg, which
is equimolar to 30 mg/kg dose of aspirin).
Figure 8. Release of aspirin from prodrug 1-DI-RI in Simulated Gastric
Fluid (SGF); Pooled data (n = 2); A) Line graph; B) Bar graph.
Figure 9. Stability of aspirin (1 mM)/ Release of aspirin from 1-DI-RI (1
mM) in Simulated Intestinal Fluid (SIF); Pooled data (n = 2); A) Line graph;
B) Bar graph.
Figure 10. Degradation of aspirin (100 .M) and release of aspirin from
aspirin prodrug I-D1-R1 (NO-aspirin, 100 p,M) in human plasma; Pooled
data (n = 2); A) Line graph; B) Bar graph.
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Figure 11. Release of salicylic acid from aspirin (100 tiM) and its prodrug I-
D1-R1 (100 tiM) in human plasma; Pooled data (n = 2); A) Line graph; B)
Bar graph.
Figure 12. Stability of chlorambucil (50 LM)/ Release of chlorambucil from
I-D3-R1 (50 M) in Simulated Gastric Fluid (SGF); Pooled data (n = 3); A)
Line graph; B) Table.
DETAILED DESCRIPTION OF THE INVENTION
The present invention encompasses compounds of formula (I), as
described herein, which are nitric oxide releasing prodrugs of known
carboxyl-containing drugs or therapeutic agents useful in the treatment of
diseases or disorders that are characteristic of the drugs from which the
prodrugs of the present invention are derived.
0 H Ry
AN, X ON 2
Dx 0 0
(I)
In general, the present invention provides prodrugs of known drugs or
therapeutic agents represented herein by the compounds of formula (I)
which primarily constitutes the following elements:
(a) a drug or a therapeutic agent containing at least one carboxylic
acid group [i.e., DxCO21-1] that is covalently bonded to one side of
the linker;
(b) a linker [i.e., C(H)(Ry)]; and
(c) a nitrooxy (0NO2) group covalently bonded to the other side of the
linker;
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The strategy for providing the prodrugs represented herein by the
compounds of formula (I) is applicable to any drug or therapeutic agent
which possesses a carboxylic acid functional group capable of forming a
covalent ester bond to a specified linker. The linker is a bi-functional
moiety having the desired covalent binding properties.
The prodrugs, i.e., the compounds of formula (I) of the present invention,
would undergo either chemical or enzymatic cleavage in a manner such
that the parent drugs and effective amounts of nitric oxide are released in
vivo. Also, the prodrugs of the present invention [i.e. the compounds of
formula (I)] are expected to be safe to administer and seem to have the
potential to exhibit comparable or superior oral bioavailability to that of
the
parent drug molecule.
Although the compounds of formula (I) of the present invention are derived
from the drugs or therapeutic agents containing at least one carboxylic
acid group, many such drugs or therapeutic agents may contain other
reactive functional groups such as an amino, additional carboxyl, hydroxyl
(including phenolic), sulfhydryl, phosphate, aldehyde and keto (in the form
of their derivatives such as oxime, hydrazone, semicarbazone and the like)
groups or a mixture of one or more types of these functional groups. As a
result, the compounds of formula (I) could also be represented by the
following alternative formula I-a:
0 H Ry
(HX), )1 X ,)102
---Dx 0 0
(I-a)
Wherein,
(HX)-Dx-C(=0)0 represents a drug or therapeutic agent containing at
least one carboxylic acid group, which is covalently bonded to the
specified linker "C(H)(Ry)" via a bio-cleavable ester linkage; where
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X independently at each occurrence represents 0 (i.e., corresponds to a
primary, secondary, tertiary or phenolic hydroxyl group), S (i.e.,
corresponds to a primary, secondary, tertiary or thiophenolic sulfhydryl
group), carboxylate (i.e., CO2"), amino group (i.e., NH or N, which
represent primary or secondary amino groups, respectively), a phosphate
[i.e., P(=0)(0-)2], a carbonyl group (i.e., an aldehyde or keto group in the
form of their bio-cleavable derivatives such as an oxime, hydrazone,
semicarbazone and the like) or a mix of one or more types of these
functional groups;
n represents 0 (zero) or 1-20, preferably 0 (zero) or 1-10, yet preferably 0
(zero) or 1-5, yet most preferably 0 (zero) or 1-2;
Ry is an alkyl C1_C6 or cycloalkyl C3_C7; preferably alkyl C1.C.4; yet
preferably alkyl C1_C2; yet most preferably alkyl Ci (i.e., CH3);
0NO2 (i.e., nitrooxy) group is covalently bonded to the other side of the
linker;
and in all its geometrical and stereoisomeric forms and also
pharmaceutically acceptable salts thereof;
Also encompassed within the scope of the invention represented by the
formula (I) are the compounds of the invention, wherein, the drug or
therapeutic agent contains, in addition to the required one carboxylic acid
functional group, one or more other reactive functional groups such as an
amino, a hydroxyl (including phenolic and hydroxyl group of oxime
derivative of a carbonyl group of an aldehyde or keto group), a sulfhydryl,
a phosphate or additional carboxyl group(s), or a mixture of one or more
types of the said functional groups and these additional functional groups
have to be specifically protected, if necessary, by appropriate bio-
cleavable protecting groups (zPGs); Consequently, the compounds of
formula (I) could also be represented by the following alternative formula I-
b:
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0 H Ry
(1PG-X)riN X NO2
Dx 0 0
(I-b)
Wherein,
X}PG represents 0-hPG, S-sPG, C(=0)0-cPG, NH-aPG, N-aPG or
[P(=0)(0-PPG)2], where
hPG represents a bio-cleavable hydroxyl protecting group such as acetyl
group and the like;
'PG represents a bio-cleavable sulfhydryl protecting group such as acetyl
group, disulfide bond and the like;
cPG represents a bio-cleavable carboxyl protecting group such as lower
(alkyl C1-C6) alkyl esters and the like;
aPG represents a bio-cleavable amino protecting group such as acetyl,
ethoxycarbonyl, 2-acetylthioethoxycarbonyl or 2-(2-
aminoethyl)dithioethoxy-carbonyl group and the like;
PG represents a bio-cleavable phosphate protecting group such as 2-(S-
acetylthio)ethyl (SATE), 3-pivaloyloxy-1,3-dihydroxypropyl derivative,
dithiodiethanol derivative, 4-acyloxybenzyl phosphate mono or diester
derivatives and the like;
and the remaining elements of the formula (I) (or I-a or 1-b) are same as
defined above;
A good example of one such drug is aspirin, i.e., o-acetyl salicylic acid,
wherein the anti-inflammatory drug salicylic acid has, in addition to the
required one carboxylic acid group, one additional reactive phenolic
hydroxyl group, which is protected by the bio-cleavable acetyl group.
.. Unless otherwise indicated, the following definitions are set forth to
illustrate and define the meaning and scope of various terms used to
describe the invention herein and the claims. These definitions should not
be interpreted in the literal sense as they are not general definitions and
are relevant only for this application.
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As used herein, the term "prodrug or prodrugs" refers/refer to a
compound/compounds which upon administration to a subject in need
thereof undergoes cleavage in vivo either by enzymatic or chemical
processes to release the parent drug from which the prodrug is derived.
As used herein, the terms "drug" or "drugs" 'or "therapeutic agents" or
"drug molecules" or "parent drug" or "parent drug molecules", which are
represented by the symbols "Dx" or "Dx-C(=0)0" or "(HX),-Dx-C(=0)0" or
"(HX),-Dx-C(=0)0" or "CPG-X)n-Dx-C(=0)0" [where zPG represent an
appropriate bio-cleavable protecting group for an amino (aPG) or a
hydroxyl (hPG) or a sulfhydryl (aPG) or a carboxyl (CPG) or a phosphate
(PPG) group] are used interchangeably when n represents 0 (zero). The
term "drug" or "therapeutic agent" as used herein refers to any compound,
substance, medicament or active ingredient having a therapeutic or
pharmacological effect, and which is suitable for administration to a
mammal, e.g., a human, more particularly, in the context of the present
invention, all the known drugs or therapeutic agents containing at least
one carboxylic acid functional group that is capable of forming a covalent
.. biocleavable ester linkage with a specified linker. The term "drug" or
"therapeutic agent" as used herein also encompasses within its scope the
"investigational drug(s)" or "investigational agent(s)" which refer to any
new drug or agent currently under clinical investigation, particularly those
investigational drugs or agents that contain at least one carboxylic acid
group that is capable of forming a covalent biocleavable ester linkage with
a linker, which may later be established as therapeutically active agent by
the regulatory bodies of different countries. As stated above, such drugs or
therapeutic agents may also contain, in addition to the required one
carboxylic acid group, other reactive functional groups such as an amino,
additional carboxyl, hydroxyl (including phenolic), sulfhydryl, phosphate,
aldehyde and keto (or their derivatives such oxime, hydrazone,
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semicarbazone and the like) groups. It is of common understanding that
such additional reactive functional groups need to be protected, if it is
necessary, with appropriate protecting groups and again those protecting
groups may need to be removed at appropriate stages of the processes
for the synthesis of compounds of formula (I). However, it is preferable to
use such protecting groups that can be cleaved under physiological
conditions so that we can avoid the process of removal of those protecting
groups from the compounds of the invention represented by the formula
(I). Thus, the compounds for formula (I) containing additional reactive
functional groups, which are protected by appropriate bio-cleavable
protecting groups, are within the scope of this invention.
As used herein, the term "linker" or "linkers" or "biocleavable linkers" or
"spacer" or spacers" refers/refer to a chemical moiety/moieties, which
forms/form a covalent ester linkage with the reactive carboxylate group of
the drug or therapeutic agent to obtain a prodrug of the drug. This linker
may be cleaved from the prodrug by chemical means, by enzymatic
means, or by both the means. The linker may be pharmacologically inert
or may itself provide added beneficial pharmacological activity.
As used herein, the term "alkyl" means a branched or straight-chain
monovalent alkyl radical, having one to six carbon atoms such that the
alkyl group is designated as alkyl C1-C6 or C1-C6 alkyl or alkyl C1.6. This
term is further exemplified by such radicals as methyl, ethyl, n-propyl,
isopropyl, n-butyl, s-butyl, t-butyl, isobutyl, amyl, n-pentyl, neopentyl,
valeryl and the like.
As used herein, the term "amino" functional group of drugs or therapeutic
agents refer to the drugs containing, in addition to the required presence of
one carboxylic acid group, other reactive primary and secondary amines
(both acyclic and cyclic) which also include drugs containing derivatizable
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NH-containing functional groups such as amide-NH, sulfonamide-NH,
carbamate-NH, sulfamate-NH, hydrazide-NH, hydrazone-NH,
semicarbazone-NH, thiosemicarbazone-NH, urea-NH, and also
encompass drug molecules with derivatizable NH-containing heterocyclic
sub-structures such as aziridine, azitidine, dihydropyridine, indole,
imidazole, benzimidazole, thiazole, benzothiazole, oxazole, benzoxazole,
pyrrole, pyrrazole, benzopyrrozole, pyrrolidine, piperidine, triazole,
benzotriazoles, tetrazole, and benzotetrazole.
As used herein, the term "hydroxyl" or "hydroxy" functional group of drugs
or therapeutic agents refer to the drugs containing, in addition to the
required presence of one carboxylic acid group, other reactive hydroxyl
(OH) groups (i.e., these hydroxyl groups can be primary, secondary,
tertiary or phenolic in nature) including hydroxyl groups of hydroxamic
acids, aldoxime, ketoximes of carbonyl-containing (i.e., aldehyde or keto
groups) drug molecules.
As used herein, the term "sulfhydryl" functional group of drugs or
therapeutic agents refer to the drugs containing, in addition to the required
presence of one carboxylic acid group, other reactive free sulfhydryl (SH)
groups and these can be primary, secondary, tertiary and thiophenolic in
nature.
As used herein, the term "halogen" refers to fluorine, bromine, chlorine or
iodine.
As used herein, the term "halide" refers to fluoride, chloride, bromide, and
iodide.
As used herein, the term "cycloalkyl" refers to a saturated mono-, bi- or
polycyclic ring system containing a specified number of carbon atoms.
26
Unless otherwise stated, cycloalkyl rings containing 3 to 7 carbon atoms
are preferred. Representative cycloalkyl groups include cyclopropyl,
cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and the like.
As used herein, the term "bio-cleavable amino protecting group" is
intended to refer to a group that can be selectively attached to the nitrogen
atom by chemical modification of an amino group so as to selectively
inhibit participation of the amino group in chemical reactions. However,
these amino protecting groups can be cleaved in vivo either chemically
(pH dependent) or enzymatically. Exemplary bio-cleavable amino-
protecting groups include carbamates (urethanes) such as methyl, ethyl
and t-butyl (i.e., BOG or tert-butoxycarbonyl) and amides such as acetyl,
methoxyacetyl, etc. The procedures for the formation of the above
mentioned bio-cleavable amino protecting groups are based on the known
methods and their relevant references as cited in T. W. Greene,
"Protective Groups in Organic Synthesis", Third Edition, 1999, John Wiley
and Sons, New York. Additional examples of bio-cleavable amino
protecting groups are shown in Chart 2.
As used herein, the term "bio-cleavable hydroxyl protecting group" or "bio-
cleavable hydroxy protecting group" is intended to refer to a group that can
be selectively attached to the oxygen atom by chemical modification of the
hydroxyl group so as to selectively inhibit the participation of the hydroxyl
group in chemical reactions. Examples of such bio-cleavable hydroxyl and
phenolic-protecting groups include the ester groups selected from acetate
ester, methoxyacetate ester, benzoate ester, phenyl acetate ester, pivalate
ester, phenoxyacetate ester, monosuccinate, nitrate, ethyl carbonate and
methoxymethyl carbonate. The procedures for the formation of the above
mentioned bio-cleavable hydroxyl protecting groups are based on the
known methods and their relevant references as cited in T. W. Greene,
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"Protective Groups in Organic Synthesis", Third Edition, 1999, John Wiley
and Sons, New York.
As used herein, the term "bio-cleavable carboxyl protecting group" or "bio-
cleavable carboxylic acid protecting group" is intended to refer to a group
that selectively blocks the oxygen functionality within a carboxylic acid
group so as to inhibit participation of the carboxylic acid group in chemical
reactions. Examples of such carboxylic acid protecting groups include for
example unsubstituted and substituted alkyl esters such as methyl and
ethyl. The procedures for the formation of the above mentioned carboxyl
protecting groups are based on the known methods and their relevant
references as cited in T. W. Greene, "Protective Groups in Organic
Synthesis", Third Edition, 1999, John Wiley and Sons, New York.
As used herein, the term "bio-cleavable sulfhydryl protecting group" or
"bio-cleavable thiol protecting group" is intended to refer to a group that
selectively blocks the thiol (SH) functionality so as to inhibit participation
of
the thiol group in chemical reactions. Examples of such thiol protecting
groups include thioesters such as S-acetyl and S-benzoyl and
unsymmetrical disulfides such as S-ethyl disulfide and S-t-butyl disulfide.
The procedures for the formation of the above mentioned bio-cleavable
sulfhydryl protecting groups are based on the known methods and their
relevant references as cited in T. W. Greene, "Protective Groups in
Organic Synthesis", Third Edition, 1999, John Wiley and Sons, New York.
As used herein, the term "bio-cleavable phosphate protecting group" is
intended to refer to a group that selectively blocks the phosphate
[P(=0)(OH)2] functionality so as to inhibit participation of the free
phosphate group in chemical reactions. Examples of such bio-cleavable
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phosphate protecting groups include 2-(S-acetylthio)ethyl (SATE), 3-
pivaloyloxy-1, 3-dihydroxypropyl derivative, dithiodiethanol derivative, 4-
acyloxybenzyl phosphate mono or diester derivatives. The procedures for
the formation of the above mentioned bio-cleavable phosphate protecting
groups are based on the known methods and their relevant references as
cited in T. W. Greene, "Protective Groups in Organic Synthesis", Third
Edition, 1999, John Wiley and Sons, New York.
The term "pharmaceutically acceptable salts" refers to the salts of the
compound of formula (I) of the invention which are toxicologically
acceptable and pharmaceutically utilisable salts.
The compounds of formula (I), which contains a basic functionality, can be
used according to the invention in the form of their addition salts of organic
or inorganic acids. The pharmaceutically acceptable acid addition salts of
the prodrug compound of formula (I) include salts which retain the
biological effectiveness and properties of the free bases and which are not
biologically or otherwise undesirable.
Examples of suitable inorganic acids include hydrochloric acid,
hydrobromic acid, sulphuric acid, nitric acid, phosphoric acid, perchloric
acid, boric acid, and other inorganic acids known in the art. Examples of
organic acids include: acetic acid, propionic acid, glycolic acid, pyruvic
acid, oxalic acid, maleic acid, malonic acid, succinic acid, fumaric acid,
tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid,
sulfanilic acid, 2-acetoxy benzoic acid, toluenesulphonic acid, methane
sulphonic acid, ethane disulphonic acid, isethionic acid, ketoglutaric acid,
benzenesulphonic acid and other organic acids known in the art.
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The compound of formula (I), which contains additional acidic group(s),
can be used according to the invention as base addition salts. Examples of
pharmaceutically acceptable base addition salts include those salts
derived from inorganic bases such as alkali earth metal salts like sodium,
potassium, lithium, alkaline earth metal salts like calcium, magnesium,
aluminium salts or salts of organic bases such as lysine, arginine,
triethylamine, dibenzylamine, piperidine or salts with ammonia. Particularly
preferred are the ammonium salts of the prodrugs of the present invention
i.e. the compounds of formula (I).
The pharmaceutically acceptable salts of the present invention Can be
synthesized from the subject compound which contains a basic or acidic
moiety, by conventional chemical methods. Generally the salts are
prepared by contacting the free base or acid with stoichiometric amounts
or with an excess of the desired salt-forming inorganic or organic acid or
base in a suitable solvent or dispersant or by anion exchange or cation
exchange with other salts. Suitable solvents are, for example, ethyl
acetate, ether, alcohols, acetone, tetrahydrofuran (THE), dioxane or
mixtures of these solvents.
In a first embodiment, the invention relates to compounds of the formula
(I), which are prodrugs of known drugs or therapeutic agents;
0 H Ry
)c X NO2
Dx 0 0
(I)
Wherein,
Dx-C(=0)0 a drug or therapeutic agent containing at least one carboxylic
= acid group, which is covalently bonded to the specified linker "C(H)(Ry)"
via a bio-cleavable ester linkage;
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Optionally, Dx-C(=0)0 may contain, in addition to the requisite one
carboxylate group, additional reactive functional group(s) [(X)J, which may
be protected by appropriate bio-cleavable protecting groups (93Gs). As a
result, Dx-C(=0)0 can be represented alternatively as (X),-,-Dx-C(=O)O.
Thus, the compound of formula (I) could also be represented by the
following alternative formula:
0 H Ry
(X)n __)L, X NO2
(I)
Wherein,
X independently at each occurrence represents OH (i.e., a primary,
secondary, tertiary or phenolic hydroxyl group), 0-"PG, SH (i.e., a primary,
secondary, tertiary or thiophenolic sulfhydryl group), S-sPG, CO2H or
C(=0)0-`PG, amino group (i.e., NH2 or NH or N, which represent primary
or secondary or tertiary amino groups, respectively), HN-aPG, N-aPG, a
phosphate group [i.e., P(=0)(OH)2], a protected phosphate group [i.e.,
P(=0)(0-PPG)2], a carbonyl group (i.e., an aldehyde or keto group in the
form of their bio-cleavable derivatives such as an acetal, oxime,
hydrazone, semicarbazone and the like) or a mixture of one or more types
of these functional groups, where
"PG represents a bio-cleavable hydroxyl protecting group such as acetyl
group and the like;
sPG represents a bio-cleavable sulfhydryl protecting group such as acetyl
group, disulfide bond and the like;
cPG represents a bio-cleavable carboxyl protecting group such as lower
(alkyl C1-C6) alkyl esters and the like;
aPG represents a bio-cleavable amino protecting group such as acetyl,
ethoxycarbonyl, 2-acetylthioethpxycarbonyl or 2-(2-
aminoethyl)dithioethoxy-carbonyl group and the like;
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PPG represents a bio-cleavable phosphate protecting group such as 2-(S-
acetylthio)ethyl (SATE), 3-pivaloyloxy-1,3-dihydroxypropyl derivative,
dithiodiethanol derivative, 4-acyloxybenzyl phosphate mono or diester
derivatives and the like;
n represents 0 (zero) or 1-20, preferably 0 (zero) or 1-10, yet preferably 0
(zero) or 1-5, yet preferably 0 (zero) or 1-2;
Ry is an alkyl Ci_Cs or cycloalkyl C3.C7; preferably alkyl C1..C4; yet
preferably alkyl C1_C2; yet most preferably alkyl C1 (i.e., CH3);
0NO2 (i.e., nitrooxy) group is covalently bonded to the other side of the
linker;
and in all its geometrical and stereoisomeric forms and also
pharmaceutically acceptable salts thereof.
In a second embodiment, the invention encompasses a compound of
formula (I), wherein:
Dx is as defined in the first embodiment herein above;
Ry is alkyl C1-06;
and in all its geometric and stereoisomeric forms and pharmaceutically
acceptable salts thereof.
In a third embodiment, the invention encompasses a compound of formula
(I), wherein:
Dx is as defined in the first embodiment herein above;
Ry is alkyl 01-C4; yet preferably Ry is ethyl (CH2CH3); yet most preferably
.. Ry is methyl (CH3);
and in all its geometric and stereoisomeric forms and pharmaceutically
acceptable salts thereof.
In a fourth embodiment, the invention encompasses a compound of
formula (I), wherein: Dx, the drug or therapeutic agent containing a
carboxylic acid group capable of forming a covalent bio-cleavable ester
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linkage with a linker, referred to in the first, second, and third
embodiments, is selected from the group comprising of an anti-
inflammatory and analgesic agent, a cardiovascular agent, an anti-allergic
agent, an anti-cancer agent, an anti-depressant, an anti-convulsant agent,
an anti-bacterial agent, an anti-fungal agent, an agent, an anti-malarial
agent, an anti-lipidemic agent, an anti-diabetic agent, an anti-ulcer agent,
a vitamin and an anti-oxidant.
In this embodiment, other variables of Ry in the compounds of formula (I)
are as defined hereinabove;
in all its geometrical and stereoisomeric forms and pharmaceutically
acceptable salts thereof.
In a fifth embodiment, in the compound of formula (I), the anti-
inflammatory and analgesic agent referred to in the fourth embodiment
hereinabove is selected from the group comprising of aceclofenac,
acemetacin, acetamidocaproic acid, acetylsalicylsalicylic acid, actarit,
alclofenac, 3-alminoprofen, amfenac, 3-amino-4-hydroxybutyric acid,
aspirin (acetylsalycilic acid), balsalazide, bendazac, benoxaprofen,
bromprofen, bromfenac, 5-bromosalicylic acid acetate, bucloxic acid,
bumadizone, butibufen, carprofen, cinchophen, cinmetacin, clidanac,
' clometacin, clonixin, clopirac, diacerein, diclofenac, diflunisal,
dipyrocetyl,
enfenamic acid, enoxolone, etodolac, felbinac, fenbufen, fenclozic acid,
fendosal, fenoprofen, fentiazac, flufenamic acid, flunoxaprofen,
fluocortolone-21-acid, flurbiprofen, fosfosal, gentisic acid, ibufenac,
ibuprofen, indomethacin, indoprofen, isofezolac, isoxepac, ketoprofen,
ketorolac, lonazolac, loxoprofen, meclofenamic acid, mefenamic acid,
mesalamine, metiazinic acid, mofezolac, naproxen, niflumic acid,
olsalazine, oxaceprol, oxaprozin, pirazolac, pirprofen, pranoprofen,
protizinic acid, salicysulfuric acid, salicylamide o-acetic aeid, salsalate,
sulfasalazine, sulindac, suprofen, suxibuzone, tiaprofenic acid, tolfenamic
acid, tolmetin, tropesin, ximoprofen, zaltoprofen and zomepirac.
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A representative example of an anti-inflammatory and analgesic agent is a
NSAID that is selected from the group comprising of aspirin, diclofenac,
diflunisal, etodolac, fenoprofen, flurbiprofen, ibuprofen, indomethacin,
ketoprofen, ketorolac, naproxen, sulindac and tolmetin.
Further in the sixth embodiment, the invention encompasses a compound
of formula (I); wherein the cardiovascular agent referred to in the fourth
embodiment hereinabove is generically selected from the group
comprising of antihypertensive agents such as angiotensin converting
enzyme (ACE) inhibitors, beta-blockers, sartans (angiotensin II blockers),
anti-thrombotic and vasoactive agents, anti-hyperlipidemic drugs (including
HMG-CoA-reductase inhibitors (statins)), fibrates, anti-anginal agents,
anti-arrhythmic agents, anticoagulants, anti-hypotensive agents, diuretics,
vasodilators and vasoprotectants and is specifically selected from the
=
group comprising of acifran, acipimox, acetylsalicylic acid, alacepril, gama-
aminobutyric acid, angiotensin, argatroban, atorvastatin, benazepril,
benfurodil hemisuccinate, beraprost, bezafibrate, bumetanide,
candesartan, capobenic acid, captopril, carmoxirole, caronapril,
cerivastatin, chromocarb, cilazapril, ciprofibrate, clinofibrate, clofibric
acid,
dalteparin, daltroban, delapril, dextrothyroxine, eicosapentaenoic acid,
eledoisin, enalapril, enalaprilat, enoxaparin, eprosartan, ethacrynic acid,
fluvastatin, fosinopril, furosemide, gemfibrozil, iloprost, imidapril,
indobufen, isbogrel, heparin, lamifiban, lifibrol, limaprost, lisinopril,
losartan
acid (EXP-3174), lotrafiban, meglutol, melagatran, mercamphamide,
mercaptomerin sodium, mercumallylic acid, mersalyl, methyldopa,
moexipril, moveltipril, nadroparin, omapatrilat, ozagrel, oxiniacic acid,
perindopril, piretanide, pitavastatin, pravastatin sodium, prostaglandin El,
quinapril, ramipril, reviparin sodium salt, ridogrel, rosuvastatin,
sampatrilat,
saralasin, satigrel, spirapril, taprostene, telmisartan, temocapril,
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thyropropic acid, ticrynafen, tinzaparin, tirofiban, trandolapril, triflusal,
valsartan, xanthinol niacinate, xenbucin and zofenopril.
A representative example of the cardiovascular agent is an ACE-inhibitor
that is selected from the group comprising of benazepril, enalapril,
enalaprilat, lisinopril, perindopril, quinapril, ramipril, ramiprilate,
trandolapril, alacepril, captopril, ceronapril, cilazapril, delapril,
fosinopril,
imidapril, lisinopril, moexipril, moveltipril, omapatrilat, sampatrilat,
spirapril,
temocapril and zofenopril.
Another representative example of the cardiovascular agent is a sartan
that is selected from the group comprising of candesartan, olmesartan,
losartan acid (EXP-3174), telmisartan, and valsartan.
.. Yet another representative example of the cardiovascular agent is an anti-
thrombotic, anticoagulant or vasodilator agent that is selected from the
group comprising of acetylsalicylic acid (aspirin), argatroban, beraprost,
dalteparin, daltroban, enoxaparin, iloprost, indobufen, isbogrel, heparin,
lamifiban, lotrafiban, melagatran, nadroparin, ozagrel, reviparin sodium
salt, ridogrel, satigrel, taprostene, tinzaparin, tirofiban and triflusal.
Yet another representative example of the cardiovascular agent is an anti-
hyperlipidemic agent (statin and fibrate) that is selected from the group
comprising of atorvastatin, bezafibrate, cerivastatin, ciprofibrate,
.. clinofibrate, clofibric acid, clopidogrel free acid, fluvastatin,
gemfibrozil,
pitavastatin, pravastatin and rosuvastatin.
Yet another representative example of the cardiovascular agent is an anti-
anginal agent such as limaprost.
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Yet another representative example of the cardiovascular agent is an anti-
arrhythmic agent such as capobenic acid.
Yet another representative example of the cardiovascular agent is an anti-
hypotensive agent such as angiotensin II.
Yet another representative example of the cardiovascular agent is a
diuretic that is selected from the group comprising of bumetanide,
ethacrynic acid, furosemide, mercamphamide, mercaptomerin sodium,
mercumallylic acid, mersalyl, piretanide and ticrynafen.
Yet another representative example of the cardiovascular agent is a
vasodilator that is selected from the group comprising of benfurodil
hemisuccinate, beraprost, eledoisin, iloprost, prostaglandin Ei and
xanthinol niacinate.
Yet another representative example of the cardiovascular agent is a
vasoprotectant such as chromocarb.
Still further, in the seventh embodiment, the invention encompasses a
compound of formula (I); wherein the anti-allergic agent referred to in the
fourth embodiment hereinabove is generically selected from the group
comprising of a steroidal bronchodilator, a mast cell stabilizer and an anti-
histamine and is specifically selected from the group comprising of
acrivastine, amlexanox, bepotastine, cetirizine, fexofenadine,
levocetirizine, lodoxamide, montelukast sodium, nedocromil, olopatadine,
pentigetide and tranilast.
A representative example of the anti-allergic agent is an anti-histamine
that is selected from the group comprising of acrivastine, bepotastine,
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cetirizine, fexofenadine, levocabastine, levocetirizine and montelukast
sodium.
Still further, in the eighth embodiment, the invention encompasses a
compound of formula (I); wherein the anti-cancer agent referred to in the
fourth embodiment hereinabove is selected from the group comprising of
acitretin (etretin), aminolevulinic acid, amsilarotene, butyric acid,
chlorambucil, eflornithine hydrochloride, melphalan, methotrexate,
minodronate (minodronic acid), retinoic acids (including 13-cis retinoic and
all trans-retinoic acids), sulindac, tamibarotene, and valproic acid.
Still further, in the ninth embodiment, the invention encompasses a
compound of formula (I); wherein the antidepressant referred to in the
fourth embodiment hereinabove is generically selected from antimaniacs
and antipsychotic agents and is specifically selected from the group
comprising of amineptine, gabapentin, 5-hydroxytryptophan (oxitriptan),
pregabalin, tianeptine, valproic acid and vigabatrin. -
Still further, in the tenth embodiment, the invention encompasses a
compound of formula (I); wherein the anticonvulsant referred to in the
fourth embodiment hereinabove is selected from the group comprising of
gabapentin, pregabalin, tiagabine, valproic acid and vigabatrin.
Still further, in the eleventh embodiment, the invention encompasses a
compound of formula (I); wherein the anti-bacterial agent referred to in the
fourth embodiment hereinabove is selected from the group comprising of
acediasulfone, amdinocillin, p-aminosalicylic acid,
amoxicillin,
amphomycin, ampicillin, apalcillin, apicycline, aspoxicillin, azidocillin,
azlocillin, aztreonam, bacitracin, balofloxacin, benzoylpas, benzylpenicillin,
betamipron, biapenem, carbenicillin, carindacillin, carumonam, cefaclor,
cefadroxil, cefalexin, cefamandole, cefatiam, cefatrizine, cefazedone,
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cefazolin, cefbuperazone, cefclidin, cefdinir, cefditoren, cefepime,
cefetamet, cefixime, cefmenoxime, cefmetazole, cefminox, cefodizime,
cefonicid, cefoperazone, ceforanide, cefoselis, cefotaxime, cefotetan,
cefotiam, cefoxitin, cefozopran, cefpimizole, cefpiramide, cefpirome,
cefroxadine, cefsulodin, ceftazidime, cefteram, ceftezole, ceftibuten,
ceftizoxime, ceftriaxone, cefprozil, cefuroxime, cefuzonam, cephacetrile
sodium, cephalexin, cephaloglycin, cephaloridine, cephalosporin C,
cephalothin, cephapirin sodium, cephradine, cilastatin, cinoxacin,
ciproflaxacin, clavulinic acid, clavulanate, clinafloxacin, clometocillin,
cyclacillin, dicloxacillin, difloxacin, enoxacin, epicillin, ertapenem,
fenbenicillin, fleroxacin, flomoxef, floxacillin, flumequine, fosfomycin,
fropenem, fusidic acid, garenoxacin, gatifloxacin, gemifloxacin,
grepafloxacin, hetacillin, hydnocarpic acid, imipenem, lomefloxacin,
loracarbef, lymecycline, merbromin, meropenem, metampicillin, methicillin,
mezlocillin, miloxacin, moxalactam, moxifloxacin, nadifloxacin, nafcillin,
nalidixic acid, negamycin, noprysulfamide, norfloxacin, ofloxacin,
opiniazide, oxacillin, oxolinic acid, pan ipenem, pazufloxacin, pefloxacin,
penicillin(s), penimepicycline, phenethicillin, phthalylsulfacetamide,
phthalylsulfathiazole, pipemidic acid, piperacillin, piromidic acid,
propicillin,
prulifloxacin, quinacillin, ritipenem, rosoxacin, rufloxacin,
salazosulfadimidine, salbactam,
sitafloxacin, sparfloxacin,
succinylsulfathiazole, succisulfone,
sulbenicillin, sulfachrysoidine,
sulfaloxic acid, 4-sulfanilamidosalicylic acid, sulfanilic acid, tazobactam,
teicoplan in, temocillin, ticarcillin, tigemonam, tosufloxacin, trovafloxacin,
tyrocidine and vancomycin.
A representative example of the antibacterial agent is selected from the
group comprising of amoxicillin, ampicillin, cefadroxil, cefalexin, cefixime,
cefotaxime, cefuroxime, cephalexin, ciprofloxacin, gatifloxacin,
nadifloxacin, nalidixic acid, norfloxacin, ofloxacin, oxacillin, panipenem,
salbactam and vancomycin.
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Still further, in the twelfth embodiment, the invention encompasses a
compound of formula (I); wherein the anti-fungal agent referred to in the
fourth embodiment hereinabove is selected from the group comprising of
amphotericin B, azaserine, benzoic acid, candicidin, lucensomycin,
natamycin, nystatin, propionic acid, salicylic acid and undecylenic acid (10-
undecenoic acid).
Still further, in the thirteenth embodiment, the invention encompasses a
compound of formula (I); wherein the anti-viral agent referred to in the
fourth embodiment hereinabove is selected from foscarnet sodium,
Oseltamivir (Tamiflu) carboxylate (i.e., the parent drug of Tamiflu, which
contains a free carboxylic acid group) and zanamivir.
Still further, in the fourteenth embodiment, the invention encompasses a
compound of formula (I); wherein the anti-malarial agent referred to in the
fourth embodiment hereinabove is artesunate.
Still further, in the fifteenth embodiment, the invention encompasses a
compound of formula (I); wherein the anti-diabetic agent referred to in the
fourth embodiment hereinabove is selected from the group comprising of
mitiglinide, nateglinide, and repaglinide.
Still further, in the sixteenth embodiment, the invention encompasses a
compound of formula (I); wherein ,the antiulcer agent (including proton
pump inhibitors) referred to in the fourth embodiment hereinabove is
selected from the group comprising of acetoxolone, arbaprostil,
carbenoxolone, cetraxate, ecabet, S-methylmethionine, proglumide,
rebamipide, rosaprostol, rotraxate, sofalcone and trimoprostil.
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Still further, in the seventeenth embodiment, the invention encompasses a
compound of formula (I); wherein the vitamin referred to in the fourth
embodiment hereinabove is selected from the group comprising of biotin
(vitamin H or coenzyme R), folic acid (vitamin M), menadoxime, nicotinic
acid (niacin), pantothenic acid or vitamin B5 (a member of the B complex
vitamins).
Still further, in the eighteenth embodiment, the invention encompasses a
compound of formula (I); wherein the antioxidant (including free radical
scavengers) referred to in fourth embodiment hereinabove is selected from
the group comprising of a-lipoic acid, L-Carnitine, N-acetyl L-cysteine, N-
acetyl carnosine, raxofelast, tetomilast, and SCMC-Lys (S-carboxymethylL
L-cysteine Lysine salt. H20).
For the purpose of this invention, the eighteenth embodiment also
encompasses a compound of formula (I); wherein the drug containing
carboxylic acid group is generically selected from the drugs that fall under
several other therapeutic areas (including those drugs that are classified
on the basis of their mechanism of action) and is specifically selected from
the group comprising of an abortifacient/ interceptive such as
prostaglandin E2; an anesthetic selected from the group comprising of
ecgonidine, ecgonine, hydroxydione sodium and gamma-hydroxybutyrate
(gamma-hydroxybutyric acid); an anthelmintic selected from a group
comprising of antimony sodium thioglycollate, kainic acid and stibocaptate;
an anti-acne agent selected from the group comprising of adapalene,
isotretinoin and all-trans retinoic acid; an anti-amoebic agent selected from
thiocarbamizine, and thiocarbarsone; an anti-arthritic or anti-rheumatic
agent selected from the group comprising of actarit, bucillamine, diacerein,
gold sodium thiomalate, lobenzarit, allocupreide sodium, .clobuzarit and
penicillamine; an anti-asthmatic agent selected from the group comprising
of amlexanox, cilomilast (ariflo), cromolyn, domitroban, montelukast,
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nedocromil, ramatroban and seratrodast; an anti-gout/uricosuric agent
selected from the group comprising of carprofen, probenecid, orotic acid,
oxycinchophen and ticrynafen; an anti-diuretic agent such as
oxycinchophen; an anti-glaucoma agent such as unoprostone; an anti-
hypothyroid agent selected from tiratricol and thyroxine; an anti-prostatic
hypertrophy agent such as epristeride; an anti-protozoal agent selected
from eflornithine or fumagillin; an anti-psoriatic agent such acitretin; an
anti-septic agent such as mandelic acid; an anxiolytic agent selected from
calcium n-carbamoylaspartate or clorazepic acid (i.e., clorazepate); an
astringent such as bismuth subgallate; a cathartic/laxative such as
sennoside; choleretic agent selected from the group comprising of cholic
acid, cicrotoic acid, clanobutin, cyclobutyrol, cynarin(e), dehydrocholic
acid, deoxycholic acid, dimecrotic acid, exiproben, fencibutirol,
florantyrone, menbutone, 3-(o-methoxyphenyI)-2-phenylacrylic acid,
sincalide, tocamphyl and trepibutone; an enzyme cofactor such as
pantothenic acid; an estrogen such as methallenestril; a gastroprokinetic
agent selected from alvimopan or loxiglumide; a hemostatic agent selected
from c-aminocaproic acid or tranexamic acid; a hepatoprotectant selected
from the group comprising of S-adenosyl methionine, betaine, orazamide,
timonacic (thioproline), methionine, protoporphyrin IX, thioctic acid and
tiopronin; an immunomodulator selected from the group comprising of
bucillamine, ubenimex, pidotimod, procodazole, romurtide and
thymopentin; immunosuppressant selected from brequinar or
mycophenolic acid; a mucolytic selected from the group comprising of
acetylcysteine, carbocysteine, erdosteine, letosteine and stepronin; a
muscle relaxant such as baclofen ; a nootropic/cognitive enhancer
selected from the group comprising of acetylcarnitine, hexacyclonate
sodium and leteprinim; a prostaglandin analog selected from the group
comprising of beraprost, carboprost, limaprost, prostacyclin, prostaglandin
El, prostaglandin E2, prostaglandin F2a, rosaprostol, sulprostone,
trimoprostil and Unoprostone; a sedative/hypnotic chloral selected from
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betainem or calcium 2-ethylbutanoate; a dopamine receptor agonist such
as carmoxirole; a 5a-Reductase inhibitor such as epristeride; a reverse
transcriptase inhibitor such as foscarnet sodium; thromboxane A2-receptor
antagonist selected from the group comprising of altroban, domitroban,
ramatroban, ridogrel and seratrodast and a thromboxane A2-synthase
inhibitor selected from the group comprising of isbogrel, ozagrel and
ridog rel.
Still further, in the nineteenth embodiment, is provided a pharmaceutical
composition comprising a therapeutically effective amount of a compound
of formula (I) and a therapeutically effective amount of an anti-ulcer agent
such as a proton-pump inhibitor (PPI) or a H2 receptor antagonist
(especially for chronic NSAID use), and a pharmaceutically acceptable
carrier.
It is well known that long-term NSAID users are at increased risk of
stomach ulcers, which is often a deterrent to long-term treatment. Acid
control can reduce this risk and concomitant use of an anti-ulcer agent
such as a proton pump inhibitor or a H2 receptor antagonist can thus be
beneficial in reducing the incidence of ulcers associated with chronic
NSAID use.
Thus, in the above embodiment, is provided a pharmaceutical composition
comprising a therapeutically effective amount of a compound of formula (I)
that are derived from known anti-inflammatory agents such as aspirin,
naproxen, diclofenac, indomethacin, ibuprofen and the like and a
therapeutically effective amounts of an anti-ulcer agent such as a proton-
pump inhibitor (PPI) or a H2 receptor antagonist (especially for chronic
NSAID use), and a pharmaceutically acceptable carrier.
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A representative example of the proton-pump inhibitor (PPI) is selected
from the group comprising of omeprazole, esomeprazole, lansoprazole,
rabeprazole, pantoprazole, tenatoprazole and ilaprazole. Included within
these examples are salts, isomers, racemic compounds, crystals,
polymorphs, amorphous forms and cocrystals of these examples.
A representative example of the H2 receptor antagonist is selected from
the group comprising of cimetidine, famotidine, nizatidine and ranitidine.
Included within these examples are salts, isomers, racemic compounds,
crystals, polymorphs, amorphous forms and cocrystals of these examples.
It is understandable to those skilled in the art to whom this invention
relates that the only requirement for a drug or therapeutic agent to qualify
itself as a suitable candidate for conversion to a compound of the
invention, irrespective of its structural complexity or therapeutic use or
mechanism of action, is the presence of at least one carboxylic acid
functional group in its structure. Thus, in an embodiment, the following
prophetic examples are provided to amply illustrate the scope of the
invention covering/encompassing the compounds of formula (I), wherein,
the groups Ry, hPG,SPG cPG, aPG and PPG are same as defined in the
forgoing embodiments:
OMe
CI
0 RY 0 RY N¨/ 0 RY
0 ONO2
0 ONO2
0 ONO2
0 0
CH3 CH3 CH3
I-D4-Ry I-D5-Ry I-D6-Ry
(NO-Flurbiprofen - An NSAID) (NO-Ketoprofen - An NSAID) (NO-Indomethacin
- An NSAID)
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h pG
0 Ry ''0 o
Ry
0 Ry ,L go )..
0 Ry CI
H 0, ,ONO2 0
ONO2
* .)
0 ONO2 / \ N
N 0 ONO2 1110 *
CH3 0 CI a pG ...... NH
I-D7-Ry I-D8-Ry I-D9-Ry 1-DI 0-RI
(NO-Ibuprofene - (NO-Ketorolac - (NO-Diclofenac - (NO-
Mesalamine -
An NSAID) An NSAID) An NSAID) An NSAID)
aPG
HN/
o Ry
H3C,,..0õA ...-1-., Hs,91. RY CH3 0 Ry
O ONO2 /L. .....L.,...)......)., ).....,
aPG"- N
0 ONO2 I-13C 0 ONO2
H3C
1-1311-Ry I-D12-Ry I-D13-Ry
(NO-Valproic Acid - An (NO-Gabapentin - An (NO-
Pregabalin - An
anti-epileptic agent) anti-epileptic agent)
anti-epileptic agent)
,
H
0 Ry
ji
CH3
O Ry 6.1X-------N
=
0710NO2 S
H3C '' S
aPG
"NH
I-D14-Ry I-D16-Ry
(NO-Vigabatrin - An (NO-Tiagabine - An
anti-epileptic agent) anti-epileptic agent)
s
0 0
N I F
H 0 F
/ \
N 0-hPG
0
N. / OyONO2 Ry
0-hPG 0 Ry . . \ \ . _ 0-hFG
0.h pG 0--cONO2
hPG-0"'
0 ONO2 -
a_hpG E- 0 Ry
N .
).___ '
I-D16-Ry I-017-Ry I-D18-Ry
(NO-Atorvastatin - A HMG- (NO-Cerivastatin - A HMG- (NO-Fluvastatin -
A HMG-
CoA-reductase inhibitor) CoA-reductase inhibitor) CoA-reductase
inhibitor)
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0 0,ONO2
F hPG-0 I CH3 F
:
hPG-0 . Ry 0,. NI N
0....,,,ONO2 0 ,S\ 74, i
00NO2
1 . . H '
appdE 0 Ry o
o_hpGi 0 Ry
0-"PG -hPG
hPG-0 0
I-D19-Ry I-D20-Ry I-D21-Ry
(NO-Pitavastatin - A HMG- (NO-Pravastatin - A HMG-
(NO-Rosuvastatin - A HMG-
CoA-reductase inhibitor) CoA-reductase inhibitor) - CoA-reductase
inhibitor)
CI aik, . CH3 H3C CH3
H . .
trl N Alm H3C CH3 CI HC CH3 0
0,,70NO2
0 oy.,,,,,,ONO2 op n I
IL. 0) =-=y 0 .,,,ONO 2 CI
n i n 1 v Ry
Li Ry Li Ry CH3
I-D22-Ry I-D23-Ry I-024-Ry
(NO-Bezafibrate - A (NO-Ciprofibrate - A (NO-Gemfibrozil - A
hypolipidemic agent) hypolipidemic agent) hypolipidemic agent)
NH-8PG
CH3
Et0 0 CH3
H1, .).41-:r1N 4-1 o 'PG-0 0 4 ,,o.
Ry
0 N
H 0
0 Ry
NO2
H
lb H/, ,H.N
N 0 . 0 ).---ON 02 0'." , 0). ONO2
R
I-D25-Ry I-D26-Ry Y I-D27-Ry
(NO-Enalapril - An (NO-Lisinopril - An (NO-
Captopril - An
ACE inhibitor) ACE inhibitor) ACE inhibitor)
H3C ..."---11-13C CH3
H3C N , CI
apGH3C--\ N lik
µ ...., =
aPG N
0 ONO,
0.,ONO2aP.G\ N----"---ci----ii-- y -
0 N 0 \ '..'N
N-N ONO2 N-N ,., J N-N 0 Ry
l..) Ry N , N
Ry
I-D28-Ry I-D29-Ry I-D30-Ry
(NO-Candesartan - . (NO-Valsartan - An [NO-
Losartan acid (EXP-3174) -
An angiotensin II angiotensin II An angiotensin II
receptor
receptor antagonist) receptor antagonist) antagonist]
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0
H Ry
0NO2
PN
N7.,1r0õI
r
HN
H3C H
43 HN ) 4It -
A 0 " FRY
H3C ¨ 0
aPG¨NH
I-D31-Ry I-D32-Ry
(NO-Iloprost - A vasodilator) (NO-Melagatran - An anticoagulant)
H
N(0,(0NO2 aPG OAc 0 Ry
,N
1 01110 "µN-SCH3
6n0
is io ,C F3 0 Ry 0 0 0
0 0 01\102
"LONO2 F3C
I-D33-Ry I-D34-Ry Ry I-D35-
Ry
(NO-Ridogrel - An (NO-Tirpfiban - An (NO-
Triflusal - An
antiplatelet agent) antiplatelet agent) antiplatelet: agent)
0y0NO2
H3C o
Nõ,....,,.._
OyON 02
,-- \-- H3C0 so
(3...,.. H3C0 0 Ry
hpG o_hpG
OCH3
1-1336-Ry I-D37-Ry
(NO-Limaprost - An anti-anginal agent) (NO-Capobenic acid - An anti-
arrhythmic agent)
. 0 Cl 0 Cl
- CI CI
H3C --....
CH2 ,---...0y0NO2 \ S 0-,,,,r0y0NO2
0
0 Ry 0 Ry
I-D38-Ry I-039-Ry
(NO-Etacrynic acid - A diuretic agent) (NO-
Ticrynafen - A diuretic agent)
0 Ry
CI 0,}1.,_ )- hpG,.....
r-"N-'-- o oNo2 0
N.s.,) "PG-0 0 Ry
N
0".10NO2
Me Me
I-D40-Ry I-D41-Ry
(NO-Cetirizine - An anti-histamine) (NO-Fexofenadine - An anti-
histamine)
.
,-
46
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H2N - N
yN CH3yx si N...., .
i
o Ry ' 0 Ry
CI N N N
0ONO2
N = HN NH2
0 ONO2
-'aPG 0 õ,.õ.
CI -_,) 0 0¨cPG
I-D42-Ry I-D43-Ry
(NO-Mephalan - An anticancer agent) (NO-Methotrexate - An anticancer
agent)
aPG CI aPG
I I
N...._õ---....õ......õ---... (:),....r.ONO2 N
0..õ,..0NO2
(:),S. I
0 Ry 0/ ,N / \ 0 Ry
H3C ---
I-D44-Ry I-D45-Ry
(NO-Amineptine - An antidepressnat) (NO-
Tianeptine - An antidepressnat)
='; 0 Ry 0 Ry
ok,
hpG S \'' 0 ONO2 S N.µ 0
ONO2 0 0 Ry
I 00 0 sy_NL F
abi
(I\I N I 0-)0NO2
0 0
H 0 . N 0 t\l,)
A
- - H
aPG¨K1H aPG-1711-1 aPG
I-D46-Ry I-D47-Ry I-D48-Ry
(NO-Amoxcillin - An (NO-Ampicillin - An (NO-
Ciprofloxacin - An
anti-bacterial agent) anti-bacterial agent) anti-bacterial
agent)
on
n
-,,' `-' hpG
0
f hpG hpd ..pG õpG H õ I
ihb.x(r)
hp,-2ci
.... ,.,..
o/
hpG
r s' OV
HN-...apG
!-D49-Ry
(NO-Amphotericin B - An anti-fungal agent)
47
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'
hprz
7' '''
0
hpG
0 0- hPG1
1
0 0 0 0....,ONO2
hpG' hpd' hpG
,,
Li Ry '
,
0\µ 0
HN,
'PG HN
' aPG
I-D50-Ry
(NO-Candicidin - An anti-fungal agent)
--c 0.
0 %()PG
HNA NH
0
0 0 02 H Y N
H
HN jCIN'..-.-r' N 0 Ry
litstitr 0.,T,ONO2
..õ.1.k. ,....,' .===. H
H2N N 0 Ry¨N .
I-D51-Ry , I-D52-Ry
= (NO-
Folic acid - A vitamin) (NO-Biotin - A vitamin)
=
h PG
hpG , 0 Ry
0...}-... 0 Ry
0,
uvr{ 1 0 ONO2
H 0 hp , I õ, 0 ONO2
ri 0 0 HNIIrs"/-- 07 0
js,N H-Ki,s_ NH2
2 0 HN -
./00 ON0
H :- Y cH3 il
- OjNcHH1\-13 .aPG
0 Ry NH
I-D53-Ry I-D54-Ry I-D55-Ry
(NO-Artesunate - (NO-Zanamivir -
(NO-Oseltamivir (Tamiflu) carboxylate -
Anti-malarial agent) An anti-viral agent) An anti-
influenza drug)
. o Ry
c61N
0 Ry 0-
--L'ONO2
0 Ry
0"--L'0NO2 0 -
PPG---..0 II ),...,
O'`=
\ H
PG
N
,-(:)-p-"---0 ONO2 0 H
II
0 .
,
I-D56-Ry I-D57-Ry I-D58-Ry
(NO-Zanamivir - (NO-Mitiglinide - An (NO-Repaglinide - An
An anti-viral agent) anti-diabetic agent) anti-diabetic
agent)
=
48
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Ry 0
02N0---L
00
O 1111) 's
. 02NO.,
0 ' I 0
Ry N 0 o 3c H3
0 0 H
)L 0 Ry
H3C 0
RI . N 0
H H36
6`hPG CH3
I-D59-Ry I-D60-Ry I-D61-Ry
(NO-Acetoxolone - (NO-Rebamipide - (NO-
Trimoprostil -
An anti-ulcer agent) An anti-ulcer agent) An anti-
ulcer agent)
Ry C
Ry
0
H H H3 0 )--- N 2
0 Ry H3CyNl ,..,,Jt, )- H3C y0
0
. 0 ONO2
(
.").40'-=¨/\--)COONO2 0 0 --.N
H3C 0
tl._ ,>
s--S N CH3
I-D62-Ry I-D63-Ry I-064-Ry "
(NO-alfa-Lipoic acid - (NO-Acetylcarnosine - (NO-
Raxofelast -
An antioxidant) An antioxidant) An antioxidant)
0 Ry .
Ry Ry
0
,.........,r)---00NO2
0 >--0NO2 0 )-0NO2
KIiL.CH3
H3C¨N \ H3C ¨N 0
-hpG
.:
hpG ____(3-
7.--
u- hpG I-D66-Ry I-D67-Ry
= I-065-Ry ' (NO-Ecgonidine -
An (NO-Ecgonine - An
5 (NO-Prostaglandin E2 - An interceptive agent)
anesthetic agent) anesthetic agent)
,
¨/ 0Y ONO2 ¨/
----- _________ .---ir -: ---)i, - o ,e
PG
Ry and/or CN) ) 00NO2
N 'cl"G I
ap6 0 apo 0 Ry
I-D68a-Ry I-D68b-Ry
(NO-Kainic acid - An (NO-Kainic acid - An
anthelmintic agent) anthelmintic agent)
49
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0 Ry
110111110 OLONO2
H3C-õ,0
410
CH3 ,CH3 0 Ry
H3C CH3
II .
I,-
cH3....., ...
0.-LoNO2
I-D69-Ry 1-D70-Ry
(NO-Adapalene - An anti-acne agent) (NO-All-trans-retinoic acid -
An anti-acne agent)
Ry
0--<
0 ONO2 0
sJ-0
HN' * As,SHN * As ' Ry ,
C) * C) S cPG
NH2 NH2 0
, 0
0
, O-cPG
I-071-Ry I-D72-Ry
(NO-Thiocarbamizine - (NO-Thiocarbarsone -
An anti-amoebic agent) An anti-amoebic agent)
0 o
o H3cAo 0 OACH3
F130\ 1 C Ry
RI Y
0
HN . )------ONO2 co,,,,,ONO2 sPG.$).
,..., 1 Ry 8PG_ 0
ONO2
0 Ry
CH3 k..) 0 _...-F1H
I-D73-Ry I-D74-Ry I-D76-Ry
(NO-Actarit - An anti- (NO-Diacerein - An (NO-
Penicillamine - An
arthritic agent) anti-arthritic agent) anti-arthritic
agent)
0
Ry
aPG
1.>5-1-0NO2
I 0 Ry
,ON
I .; 0.0NO2
N-
0 ONO2
0 _ I
t...) Ry hpGp
0
I-D76-Ry I-D77-Ry I-078-Ry
(NO-Amlexanox - Anti- (NO-Montelukast - Anti- (NO-Seratrodast -
Anti-
asthmatic agent) asthmatic agent) asthmatic agent)
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Ry 0 Ry 0 .
CI N 0 )-0NO2
L.)
0 = 0"--L'0NO2 HN
.., I 0,....1õ20NO2
,....,.,,N
CH3 ,s 0 N
1 // H
aPG 00 0 Ry
I-D79-Ry 1-12180-Ry I-D81 -
Ry
(NO-Carprofen - An (NO-Probenecid - (NO-Orotic acid -
An
anti-gout agent) An anti-gout agent) anti-gout agent)
Ry0NO2 0 Ry H
I ;PG '"-- N
0 0 0 0 ONO2
hpG 02N0y0
N<
-: õ\\,............"
_
P
N --.
hpG_o-
0 Ry 0
I-082-Ry I-D83-Ry I-D84-Ry
(NO-Oxycinchophen - (NO-Unopiostone - An (NO-
Epristeride - An anti-
An anti-diuretic agent) anti-glaucoma agent) prostatic
hypertrophy agent)
I I 0 Ry
õ pG õ0 1 0,..õ. õpG0NO2 ,0 1101 I
.. .
I .. CY-CONO2
io
0 Ry I ,NH
0 0 aPG-
I I
I-D85-Ry I-1386-Ry
(NO-Tiratricol - An anti-hypothyroid agent) (NO-Thyroxine - An anti-
hypothyroid agent)
,-....-. H3C H3C
0 F H
CH3
0
CHF2 0 Ry
aPG¨NI-1 0 Ry 't
H
aRG--N ./,../..1')(00NO2 'PG¨ ,y(...01.. ./ - /OCH3
:7- I N oNO2
aPG ¨NH 0 Ry and H CHF2 0
I-D87-Ry I-1388-Ry I-D89-Ry
(NO-R-eflornithine - An (NO-S-eflornithine - An (NO-
Fumagillin - An anti-
anti-protozoal agent) anti-protozoal agent)
protozoal agent)
0 0 Ry
0 Ry HN jYLOONO2
CH3 CH3 CH3 0 Ry 0 ,N
H3C \ \ \ \ hpG, 00NO2
0"-CONO2
CI
H3C0 CH3
I-D90-Ry I-D91-Ry I-D92-Ry
(NO-Acitretin - An anti-psoriatic agent) (NO-Mandelic acid - (NO-
Clorazepate -
An anti-septic agent) An anxiolytic
agent)
10 .
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. .,
,0 PG ,Op0,q,
hpG i hpG i
, \
0
,\
0
0 h 0 hpG
hpG / PG hpG ....
'0 0 0V A0 0 0 0r . 0/
-
15." hPG -(5-== hpG
0 02N00
cPG ' /H 0 Ry
RI Y
0 ONO2
02.0NO2
hpG.....0 hDr_.
ph, t 0 0 O= hpG and/ pf,õµo 0 0. hPG
hpG hpG
0
o , 0
% -:_-- ,h P
,,, G
"PG ----o- hpG ----..Ø-
!-093a-Ry I-D93b-Ry
(NO-Sennoside - A laxative agent) (NO-Sennoside - A laxative agent)
0 Ry
' hPG,0 4,
. '0'0NO2 H3C e Ry
0
hpG--0 -.1.. NO2 -....,...õ0 ______________________________________ T 0,,
,ONO2
o O
:.-_-
0---- 0 Ry
0\\
H 0
I-D94-Ry k - I-D95-Ry I-D96-Ry
(NO-Cholic acid - A (NO-Cyclobutyrol - A (NO-Trepibutone -
A
choleretic agent) choleretic agent) choleretic agent)
o, 0
Ry
PG
ONO2 N
HC 0 Ry CI 14.
0)1Ry . 0.__Ci 0
i_r
H I
N Cl = CI
HN .._., µCH3
0 N
0 \--/¨\ r,H
H3C0 H3C CH3 0 - -
3
I-D97-Ry I-D98-Ry I-D99-Ry
(NO-Methallenestril - An estrogen) (NO-Alvimopan - A (NO-
Loxiglumide - A
5 gastroprokinetic agent)
gastroprokinetic agent)
0 Ry
0 Ry
I Nor0 -
aPG"' LOrINONO2 HN 0 ONO2
. I-D100-Ry I-D101-Ry
(NO-e-Aminocaproic acid - (NO-Tranexamic acid -
A hemostatic agent) A hemostatic agent)
52
,
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'
hpG9, ...9 ___hpG
CH3 0 Ry
r----- CH3
S , 07CONO, H 0 Ry
-N
t--N 0
/ N.-1.--A NH .. spa.... OA ONO
S ONO2
HN\ aPG/ 0
aPG
I-D102-Ry 1-DI 03-Ry
(NO-S-adenosyl methionine - A hepatoprotectant) (NO-
Tiopronin - A hepatoprotectant)
H ' 0
Ryy0NO2 apG¨N/, HN
HN-aPG
0 sPGHN
Ry)--ONO2 H2N 0
H2NN -
,,S, ,_ )1x1 H N -
hpG : H
at HN---t>7.¨.0
sPG N
H N ,,%\--.
0....21 II ---\ 0 0 ,0 0
irl¨(3 Ry)--ONO2
I-D104-Ry Le
(NO-Bucillamine - An I-D105-Ry cIDG I-D106-Ry
immunomodulator and an (NO-Pidotimod - An (NO-Thymopentin - An
antirheumatic agent) immunomodulator) immunostimulator)
F
CH3
hpG /-CH
N 0 0.-- CH3 H3C.---N+ 3
. ,
I / H3C F 0 0,,.e.ONO H H........i<
= " 1 2 ,
aPGN 0 RY 0 '=
Ry"0NO2 (-.143 cH3 a...<Ry
0 - u Ry
0 9 I
lb 0-0NO2 CH3 0 ONO2
WI .-' CI
I -D107-Ry I-D108-Ry I-D109-Ry I-0110-Ry
(NO-Brequinar - An (NO-Mycophenolic acid - (NO-Baclofen - A
(NO-Acetylcarnitine - A
immunosuppressant) An immunosuppressant) muscle relaxant)
cognitive enhancer)
0 Ry 0 0 Ry
.,L. ...1..
cPG0' S'"*NT)L0 ONO2 02N0y0y--õ,s0.5PG 02NO 0- _....,
y I s'N"Tits'o oNo2
o __NH Ry 0 apG,NH ' Ry 0 apG..- NH
aPG and/or and/or
I-D111a-Ry I-D111b-Ry I-D111c-Ry
(NO-Carbocysteine - A , (NO-Carbocysteine - (NO-Carbocysteine -
mucolytic agent) A mucolytic agent) A mucolytic agent)
,
N
1 ' 0 Ry
0ONO2
.- ,..
I Nz_..,
ONO2
0 Ry \ N 0
I-D112-Ry ' I-D113-Ry
(NO-Isbogrel - A thromboxane (NO-Ozagrel - A thromboxane
A2-synthase inhibitor) A2-synthase inhibitor)
53
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Ry
0 --ONO2
/PG I
)\--0
N
0 ONO2
Ry Y
0 0
1
40 0 0
I-D114-Ry I-0115-Ry I-D116-Ry
(NO-Carmoxirole - A (NO-Domitroban - A thromboxane (NO-Ramatroban -
A thromboxane
dopamine receptor agonist) A2-receptor antagonist) A2-receptor
antagonist)
and all their geometrical and stereoisomeric forms and also
.. pharmaceutically acceptable salts thereof;
In a specific embodiment, the invention encompasses a Compound of
formula (I) selected from the list comprising of:
0 0
H3CAO 0 CH3 H3C'Ap 0 /CH3
ON 2 NO2
1-Di-RI I-D1-R2
(NO-Aspirin) (NO-Aspirin)
0
H3CA1 0 -7µCH3
CH3
0 0õ-NO2
T No2
I Me0 o CH3
I-D1-R3 I-D2-R1
(NO-Aspirin) (NO-Naproxen)
CH3 CH3
0
NO2 , NO2
Me0 CH3 Me0
0 I 0
I-D2-R2 1-02-R3
(NO-Naproxen) (NO-Naproxen)
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CH3 CI
0 0,,
NO2 Cf 0 CH3
\/ \ ON 2
Me() 1/4,1 13 OCY
I-D2-R4 I-D3-R1
(NO-Naproxen) (NO-Chlorambucil)
and their geometrical and stereoisomeric forms and also pharmaceutically
acceptable salts thereof;
The compounds of formula (I) may Contain a double bond, an asymmetric
or a chiral center either in the linker in the drug molecule, and therefore
can exist in different geometrical and stereoisomeric forms. In the
structures shown herein, where the stereochemistry of any particular chiral
atom is not specified, then all stereoisomers are contemplated and
included as the compounds of the invention. The term "chiral" refers to
molecules which have the property of non-superimposability of the mirror
image cohort, while the term "achiral" refers to molecules which are
superimposable on their mirror image partner. It is intended that all
stereoisomeric forms of the compounds of formula (I) of the invention,
including but not limited to, diastereomers (when a parent drug, like in
naproxen, contains a chiral centre) and enantiomers, as well as mixtures
thereof such as racemic mixtures, form part of the present invention. Thus,
compound of formula (I) according to the present invention can exist as
enantiomers, can be present in enantiomerically pure form, both as
levorotatory and as dextrorotatory antipodes, in the form of racemates and
in the form of mixtures of the two enantiomers in all ratios. In the case of
cis/trans isomerism the compound of formula (I) includes cis or trans forms
or mixtures of these forms in all ratios; preferably exists either in cis form
or trans form. The preparation of individual enantiomer or diastereomer
from the racemates of the compounds of the present invention
represented by the formula (I) can be carried out, if desired, by separation
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methods known in the art. For instance, the racemic forms can be resolved
= by physical methods, such as fractional crystallisation or separation by
chiral column chromatography. The individual optical isomers can be
synthesized in the optically pure form by the use of enzymes or through
asymmetric syntheses. If, for instance, a particular enantiomer of the
compound of formula (I) of the present invention is desired, it may be
prepared by derivatisation with a chiral auxiliary whereby the resulting
diastereomeric mixture is separated and the auxiliary group cleaved to
provide the pure desired enantiomer. In case, the compound of formula (I)
contains additional basic functional group such as amino or an acidic
functional group such as carboxyl, diastereomeric salts are formed with an
appropriate optically active acid or base, respectively. Consequently,
compounds of formula (I) can exist in enantiomeric or diastereomeric
forms or in mixtures thereof. The processes for preparation can utilize
racemates, enantiomers or diastereomers as starting materials. When
diastereomeric or enantiomeric products are prepared, they can be
separated by conventional methods for example, chromatographic
techniques or fractional crystallization.
Unless it is specifically desired, the racemic or diastereomeric mixture of
compounds of the invention represented by the formula (I) can be used
without resolving as the chirality resides in the linker portion and the
linker
would be cleaved off either chemically or enzymatically, or by both means,
to liberate the parent drug in its original form in vivo.
One aspect of the invention includes a pharmaceutical composition
comprising a therapeutically effective amount of the compound of formula
(I), or a pharmaceutically acceptable salt thereof and one or more of
pharmaceutically acceptable carriers, vehicles or diluents.
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Another aspect of the invention includes a method of treating a disease or
disorder in a human or mammal where a chronic, sustained and selective
release of the constituent drug or therapeutic agent and/or nitric oxide from
a compound of formula (I) is beneficial; comprising administering to a
mammal or a human in need of the treatment a therapeutically effective
amount of the compound of formula (I).
Yet another aspect of the invention includes a method of treating a
disease or disorder in a human or mammal where a chronic, sustained
and selective release of the constituent drug or therapeutic agent or nitric
oxide is beneficial; -comprising administering to said mammal a
therapeutically effective amount of the pharmaceutical composition
containing a compound of the formula (I).
In one aspect of the invention, the compounds of formula (I) as mentioned
in any one of the preceding embodiments for use in the treatment of a
disease or disorder where a chronic, sustained and selective release of
the constituent drug or therapeutic agent and nitric oxide contained in the
compounds of formula (I) is beneficial.
In another aspect of the invention, the pharmaceutical composition
according to the relevant preceding embodiments for use in the treatment
of a disease or disorder where a chronic, sustained and selective release
of the constituent drug or therapeutic agent and nitric oxide contained in
the compounds of formula (I) is beneficial.
Another aspect of the invention includes use of the compounds of formula
(I) as mentioned in any one of the preceding embodiments for the
treatment of a disease or disorder where a chronic, sustained and
selective release of the constituent drug or therapeutic agent and nitric
oxide contained in the compounds of formula (I) is beneficial.
57
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Yet another aspect of the invention includes use of the pharmaceutical
composition as mentioned in relevant preceding embodiments for the
treatment of a disease or disorder where a chronic, sustained and
selective release of the constituent drug or therapeutic agent and nitric
oxide contained in the compounds of formula (I) is beneficial.
Yet another aspect of the invention includes use of the compounds of
formula (I) as mentioned in any one of the preceding embodiments for the
manufacture of medicaments for the treatment of a disease or disorder
where a chronic, sustained and selective release of the constituent drug or
therapeutic agent and nitric oxide contained in the compounds of formula
(I) is beneficial.
Yet another aspect of the invention includes use of the pharmaceutical
composition as mentioned in preceding embodiments for the manufacture
of medicaments for the treatment of a disease or disorder where a chronic,
sustained and selective release of the constituent drug or therapeutic
agent and nitric oxide contained in the compounds of formula (I) is
beneficial.
According to a further aspect of the invention, there is provided a process
for producing a compound of formula (I) or a pharmaceutically acceptable
salt thereof.
The compound of formula (I) may be prepared by the method shown in
Scheme 1, wherein, the drug or therapeutic agent contains just one
carboxylic acid functional group and no other derivatizable functional
groups.
58
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Scheme 1
0 Steps 1 - 0 '
Oxalyl chloride, DMF (1 or 2 drops), DCM, RT, 3 h
Dx0H _____________________________________________ Dx=A`LG
Dx-CO2H . (or) Thionyl chloride/bromide, RT/Reflux Dx-C(=0)-LG
Wherein,
LG = Cl or Br.
Wherein, Ry-CHO
D, and Ry are same as defined in the embodiments. Steps 2 ZnCl2, DCM,
-15 C,to RT
=
0 H Ry Step3 0 H Ry
X 7NO2 AgNO3, Acetonitrile, RI or Reflux
Dx 0 0 Dx 0 LG
I-Dx-Ry Dx-Ry-LG
(I) Wherein,
LG = Cl or Br.
Step 1
In this step, the drug or therapeutic agent containing carboxylic acid group
(Dx-CO2H) is treated with carbonyl chloride, for example oxalyl chloride,
and DMF (catalytic amount), or thionyl chloride, in the presence of an
organic solvent, for example, dichloromethane to form a reactive carbonyl
derivative such as the acid chloride of formula Dx-C(=0)-LG (wherein LG
= Cl).
Step 2
The reactive acid chloride Dx-C(=0)-LG is then coupled with the aldehyde
Ry-CHO in the presence of a catalyst such as zinc chloride and a solvent
such as dichloromethane to form a compound intermediate Dx-Ry-LG.
Step 3
The compound intermediate Dx-Ry-LG is subjected to nitration using silver
nitrate in the presence of an organic solvent, for example, acetonitrile to
59
form the compound I-Dx-Ry of formula (I), and if desired, the compound of
formula (I) is converted to its pharmaceutically acceptable salt.
In Scheme 1, the variables Dx and Ry are as defined in any of the
embodiments of the present invention with reference to the compounds of
formula (I) wherein Dx is a part of drug/therapeutic agent containing at
least one carboxylic acid group.
As mentioned above, in the synthesis of compounds of invention of
formula (I), wherein, the drug or therapeutic agent contains, in addition to
the required one carboxylic acid functional group, other reactive functional
groups such as an amino, a hydroxyl (including phenolic and hydroxyl
group of oxime derivative of a carbonyl group of an aldehyde or keto
group), a sulfhydryl, a phosphate, additional carboxyl group(s) or a mixture
of one or more types of these functional groups, such reactive functional
groups should be masked with appropriate bio-cleavable protecting
groups. The methods for the formation along with their relevant references
for all the known examples of bio-cleavable amino protecting groups,
hydroxyl protecting groups, sulfhydryl protecting groups, carboxyl
protecting groups and phosphate protecting groups are listed in T. W.
Greene, "Protective Groups in Organic Synthesis", Third Edition, 1999,
John Wiley and Sons, New York.
A general method for the synthesis of compounds of invention represented
by the formula (I), wherein, the drug or therapeutic agent contains, in
addition to the required one carboxylic acid functional group, one or more
other reactive functional groups is depicted in Scheme 2.
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Scheme 2
Step 1
HX Selective protection of other functional groups with zPG-
X)n 0
( (
)n
)10H appropriate bio-cleavable protecting groups (zPG)
Dx [For details, refer to Scheme 3] I Dx
(HX),-Dx-CO2H A-1
Oxalyl chloride
DMF (1 0r2 drops)
Step 2 DCM, RI, 3 h
Or
Thionyl halide
RT/Reflux
0 H Ry Step 3 0
(zPG-X)n ___ >(:)X ZnCl2, DCM, -15 C to RT (zPG-X)n
Dx LG
Ry¨CHO rDx
A-3 A-2
AgNO3 Step 4
Acetonitrile
RI or Reflux
0 H Ry
(zPG-X)n yk,...0XcyNO2
-Dx
1-(zPG-X)n-Dx-Ry
(I)
Wherein, the variables Dx and Ry are as defined in the embodiments.
X = 0, S, NH*(i.e., represents a primary amino group), N (i.e., represents a
secondary amino group) or C(=0)0;
n represents 0 (zero) or 1-20, preferably 1-10, yet preferably 1-5, yet most
preferably 1-2;
zPG = a bio-cleavable protecting group of a hydroxyl ("PG) or sulfhydryl
(sPG) or carboxyl (cPG) or amino (aPG) or phosphate (PPG) group;
LG = Cl or Br;
Step 1
In this step, one or more reactive functional group(s) denoted by (HX)n of
.. the drug or therapeutic agent [i.e., (HX),-Dx-CO2H or simply Dx] is/are
selectively protected by a potential bio-cleavable protecting group such as,
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for example, the ethoxycarbonyl group for amino protection, the ethyl ester
for carboxyl protection, the acetyl group for hydroxyl or sulfhydryl
protection, the 2-(S-acetylthio)ethyl (SATE) group for phosphate
protection, to obtain the corresponding protected compound of formula
(zP3-X)n-Dx-CO2H (A-1).
Step 2
The protected compound of formula (PG1-X)n-Dx-CO2H (A-1) (which still
contains a free carboxylic acid group) is treated with carbonyl chloride, for
example oxalyl chloride, and DMF (catalytic amount), or thionyl chloride, in
the presence of an organic solvent, for example, dichloromethane to yield
a reactive carbonyl derivative such as the acid halide of formula (PG2-X)n-
Dx-C(=0)-LG (A-2).
Step 3
The reactive acid halide (PGz-X)n-Dx-C(=0)-LG (A-2) is then coupled with
the aldehyde Ry-CHO in the presence of a catalyst such as zinc chloride
and a solvent such as dichloromethane to form an intermediate compound
A-3.
Step 4
The intermediate compound A-3 is subjected to nitration using silver
nitrate in the presence of an organic solvent, for example, acetonitrile to
form the compound of formula (I) and if desired, the compound of formula
(I) is converted to its pharmaceutically acceptable salt.
The organic base used in the processes for the preparation of the
compound of formula (I) as depicted in the aforementioned schemes, may
be selected from but not limited to triethylamine, diisopropylethylamine, 4-
(dimethylamino) pyridine (DMAP), pyridine or mixtures thereof.
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The organic solvent used in the processes for the preparation of the
compound of formula (I) may be selected from but not limited to
dichloromethane (DCM), chloroform, dimethylformamide (DM F),
tetrahydrofuran (THF), acetonitrile, ethyl acetate, diethyl ether or mixtures
thereof.
Additional examples of bio-cleavable protecting groups, particularly, bio-
cleavable amino protecting groups, along with their method of synthesis,
are shown in Scheme 3.
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Scheme 3
0 0
RqY 0 rA,OH
'- RqyS
riCOH
0 0 Dx
Dx
A-1'1 A-18
Rq
. RqC(=0)-LG or
X = 0 [RqC(=0)]20 X = S RqC(=0)-LG or C)
Pyridine [RqC(=0)120 S
DCM Pyridine
DCM 0
0 RcIr-SO}CLG
(H4 \ 0
)t-'0H 0 1-1
I . 0 0
Dx
LG TEA, DCM Rp¨N--
Dx ---0 , X = NRp ) Dx OH
0 \
[Wherein, X =0, S, NRp \ A-1a1
(Rp is as defined) or X = NRp S¨s
C(=0)0] \
LG TEA, DCM \ 0
1-2 0---1
-----0 LG
X = NRp 0 \____\
0 0 Rp
I 0
X = NRp S
N ______________________________________________________________ )L.
R
0 Ip Dx OH
1' 0
RqõskO)t S A-1a2
0
X = NRp L--.1 TEA, DCM 1-3 0..___
" LG
1
LG LG Rp
Nr0 DxL )0c 0 0
HO..{ ....---...,,,S
Os) N 0 ,,----.70)(N1 ,_, .)c
0 1 0 r 0 I Dx OH
Rp 0
A-123
-'6-
r---1
, 1-5 ) I 0
0 Rq Rp..õs0.õN
Dx
Nr0 II 0
LG (o)
A-124
Rp Rp
0 I i 0
0,/---....s y __
.,--ON,
p 11 iDx-ikoH
Ai o (o)t o
A-125
Wherein,
Rp is as defined above;
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Rq = alkyl C1_6 or C6I-16;
r=1-4;
t = 0-2;
LG = as defined
Synthesis of intermediate A-1": The intermediate A-1" can be synthesized
by treating the therapeutic agent Dx with either alkarioic acid halide (Le.,
RqC(=0)-LG) or anhydride [i.e., [RqC(=0)]20] in the presence of a
suitable base such as pyridine in a suitable solvent such as DCM.
One of the best examples in this category of drugs is aspirin which is 0-
acetylated salicylic acid.
Synthesis of intermediate A-ls: The intermediate A-ls can be synthesized
by treating the therapeutic agent Dx with either alkanoic acid halide (i.e.,
RqC(=0)-LG) or anhydride [i.e., [RqC(=0)]20] in the presence of a
suitable base such as pyridine in a suitable solvent such as DCM.
Synthesis of intermediate A-1a1: The intermediate A-1a1 can be
synthesized by treating the therapeutic agent Dx with the reactive
intermediate I-1 (which can be freshly prepared in two steps by reacting 2-
mercaptoethanol (HSCH2CH2OH) with either alkanoic acid halide (i.e.,
RqC(=0)-LG) or. anhydride [i.e., [RqC(=0)]20] in the presence of a
suitable base such as pyridine in a suitable solvent such as DCM to afford
the S-acylated intermediate RqC(=0)SCH2CH2OH and further treating the
S-acylated intermediate with phosgene or its equivalent in the presence of
a suitable base such as pyridine in a suitable solvent such as DCM) in the
presence of a suitable base such as triethylamine in a suitable solvent
such as DCM.
Synthesis of intermediate A-1 '2:
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The intermediate A-1a2 can be synthesized by treating the therapeutic
agent Dx with the reactive intermediate 1-2 (which can be synthesized by
reacting bis-(2-hydroxyethyl)disulphide with phosgene or its equivalent in
the presence of a suitable base such as pyridine in a suitable solvent such
as DCM) in the presence of a suitable base such as triethylamine in a
suitable solvent such as DCM.
Synthesis of intermediate A-1 a3:
The intermediate A-1 a3 can be synthesized by treating the therapeutic
agent Dx with the reactive intermediate 1-3 (which can be synthesized by
reacting dialkanoic acid halide with 2-mercaptoethanol followed by
reaction with phosgene or its equivalent in the presence of a suitable base
such as pyridine in a suitable solvent such as DCM) in the presence of a
suitable base such as triethylamine in a suitable solvent such as DCM.
Synthesis of intermediate A-1":
The intermediate A-1" can be synthesized by treating the therapeutic
agent Dx with the reactive sulfone intermediate 1-4 (t = 2) (which can be
synthesized by reacting 2-(alkylthio)ethanol or 2-(phenylthio)ethanol with
phosgene or its equivalent in the presence of a suitable base such as
pyridine in a suitable solvent such as DCM to get the sulfide intermediate
(-4 (t -= 0) and further oxidation with a suitable oxidizing agent such as m-
chloroperbenzoic acid in a suitable solvent such as DCM) in the presence
of a suitable base such as triethylamine in a suitable solvent such as
DCM. Alternatively, the compound can be made by first treating the drug
Dx with the reactive sulfide intermediate 1-4 (t = 0) to get the sulfide
compound A-1" (t = 0) and its further oxidation with a suitable oxidizing
agent such as m-chloroperbenzoic acid in a suitable solvent such as DCM.
Synthesis of intermediate A-1 a5:
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=
The intermediate A-1a5 can be synthesized by treating the therapeutic
agent Dx with the reactive intermediate 1-5 (t = 2) (which can be
synthesized by reacting 2,2'-thiodiethanol with phosgene or its equivalent
in the presence of a suitable base such as pyridine in a suitable solvent
.. such as DCM and further oxidation with a suitable oxidizing agent such as
m-chloroperbenzoic acid in a suitable solvent such as DCM) in the
presence of a suitable base such as triethylamine in a suitable solvent
such as DCM. Alternatively, the compound can be made by first treating
the drug Dx with the reactive sulfide intermediate 1-5 (t = 0) to get the
sulfide compound A-1a5 (t = 0) and its further oxidation with a suitable
oxidizing agent such as m-phloroperbenzoic acid in a suitable solvent such
as DCM.
Potential examples of compounds of formula (I) containing the above
mentioned bio-cleavable amino-protecting groups (PGa) and the plausible
mechanisms of their cleavage in vivo are shown in Chart 2.
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A) Rq
0 _ Enzymatic
..õ_---' cleavage
(--- H o o
in vivo Rp ,N ).L,, OH + 0S + ,A. 0
'' _______________________________________________
(sulfhydryl-assisted 1,5-cycliztion) Dx . \__/
HO)1.., Rq
,...C....) Dx ETC AA
0 , Ry
. Rp¨N 91,,,,-..),õ NO2, + Ry-CHO +
IN03- ----.=--- NOI
Dx
________________ ,-0' CO'
)
Enzymatic (Use of alkanoylthioethoxycarbonyl group as
(1) cleavage potential bio-cleavabe amino protecting group)
0 , Rp
B)
Dx 0 I 0 , Ry =
02N/ y-=/Y N.-ic.,,s,,c:r..HA,,,,,oyN, _______ ,A,,,..---A,
NO2y
I r , S I Dx , 0 .ID
Ry ' 0 RP o ' Enzymatic Enzymatic 0
Enzymatic Enzymatic
cleavage (0 cleavage cleavage
' cleavage (Use of S,S-bis(2-(carbonyloxy)ethyl) butanebis(thioate)
group as potential bio-cleavabe amino protecting group)
in vivo
= (sulfhydryl-assisted 1,5-cycliztion)
0 H o o
HO ,N, )L., + 0)1\ S 4- Ry-CHO +
[NO3- --'- N01
, OH + RP ' ___ OH
r Dx
- 0
DCA ' Dx ETC =
. .
C)
O.) 0,/ Lox(J _c
_______________________________________________________ cv------S) ("\\ 17P
0 , Ry
/ 0 N __ r)-=)N /NO2
02N --(---,,fN OS,7) y'\,,.. Dx '
c...0
Ry ' 0 IGS- o _________ Enzymatic
Enzymatic (I) cleavage
cleavage
,
(Use of bis-2-carbonyloxyethyldisulfide group as potential bio-cleavabe amino
protecting group)
in vivo
H 0 0 (sulfhydryl-assisted
1,5-cycliztion)
Rp,,N., ,,0H + OAS + Ry-
CHO + [NO3- ---= NO
l Dx \...J
Dx ETC
D) or E) _________ (0)
,0. _____________
) Dx I ,O, 0, I I t '') Dx
,0 õco,
S '-...
02N T '''T, T NO2 Rri-- 'T.-1'0Y
NO2
,Ry ' 0 RpH H Rp 0 Ry or '1 14p 0 ' Ry
Enzymatic . a} (I) 1<..:13 Enzymatic B:--"
Enzymatic
cleavage cleavage (0 cleavage
(Use of bis-2-carbonyloxyethyldisulfide or 2-
carbonyloxyethylalkyl/phenylsulfone .
groups as potential bio-cleavabe amino protecting groups)
(Base-assisted f3-elimination)
( Cl1)t ( 0) H 0
H t + ,N rA.,
' Or
Rq,--.S r`P ) DX OH ' ,
CO2 + Ry-CHO + (NO3- ----- NO[
DVS VS Dx .
Chart 2 .
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Wherein,
AA = Released alkanoic acid such as acetic acid, propionic acid, butanoic
acid, pentanoic acid (valeric acid), hexanoic acid (capric acid) or heptanoic
acid (enanthic acid) or benzoic acid (i.e., Rq = alkyl C1_6 or C6I-15);
ETC = Released ethylene thiocarbonate;
DCA = Released dicarboxylic acid such as succinic acid, glutamic acid,
adipic acid or pimelic acid (i.e., r = 1-4);
GSH = Glutathione (reduced form);
DVS = Divinyl sulfone (I.e., t = 2);
VS = Vinyl sulfone (i.e., t = 2, Rq = as defined above);
The present invention also relates to the process of resolution of the
racemic mixture of the compound of formula (I) or a pharmaceutically
acceptable salt thereof:
The process of resolution of the racemic mixture comprises reacting the
racemic compound of formula (I) with a chiral auxiliary in the presence of a
solvent, crystallising out the desired diastereoisomeric salt and
subsequently treating it with a base to obtain the desired enantiomer of the
compound of formula (I).
The present invention furthermore relates to a pharmaceutical composition
containing a therapeutically effective amount of the compound of formula
(I) which is a nitric oxide releasing prodrug of a known drug or a
therapeutic agent or its physiologically tolerable salts, with/without a
therapeutically effective amount of an anti-ulcer agent such as a proton-
pump inhibitor (PPI) or a H2 receptor antagonist, and a pharmaceutically
acceptable carrier, and to a process for the production of the
pharmaceutical composition, which comprises converting the compound of
formula (I) into a suitable administration form using an appropriate
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pharmaceutically acceptable and physiologically tolerable excipient, and if
appropriate, using further suitable active compounds, additives or
auxiliaries.
The compound of formula (I), which are the nitric oxide releasing prodrugs
of known drugs or therapeutic agents, can be administered to a subject in
need thereof in a variety of routes such as oral, for example in the form of
pills, tablets, coated tablets, capsules, granules or elixirs. Administration,
however, can also be carried out rectally, for example in the form of
suppositories, or parentally, for example, intravenously, intramuscularly or
subcutaneously, in the form of injectable sterile solutions or suspensions,
or topically, for example in the form of solutions or transdermal patches, or
in other ways, for example in the form of aerosols or nasal sprays.
The pharmaceutical composition according to the invention is prepared in
a manner known per se, and by utilizing methods well-known to one skilled
in the art. Pharmaceutically acceptable inert inorganic and/or organic
carriers and/or additives can be used in addition to the prodrug compound
of formula (I) and/or its pharmacologically acceptable salts. For the
production of pills, tablets, coated tablets and hard gelatin capsules it is
possible to use, for example, lactose, corn starch or derivatives thereof,
gum arabic, magnesia or glucose, etc. Carriers for soft gelatin capsules
and suppositories are, for example, fats, wax, natural or hardened oils, etc.
Suitable carriers, for the production of solutions, for example, injection
solutions, or of emulsions or syrups are, for example, water, physiological
sodium chloride solution or alcohols, for example, ethanol, propanol, or
glycerol, sugar solutions, such as glucose solutions or mannitol solutions,
or a mixture of the various solvents which have been mentioned.
The pharmaceutical composition of the invention also contain additives
such as, for example, antioxidants, emulsifiers, preservatives, colouring
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agents and flavouring agents. The pharmaceutical composition also may
also contain two or more prodrug compounds of formula (I) and/or their
physiologically tolerable salts. Furthermore, in addition to at least one
prodrug compound of formula (I) and/or its physiologically tolerable salts,
the pharmaceutical composition can also contain one or more other
therapeutically or prophylactically active ingredients.
It would be understood by persons skilled in the art that the amount of the
compound of formula (I) (prodrugs of known drugs or therapeutic agents)
that is contained in the pharmaceutical composition will depend upon the
equimolar amount of the parent drug molecule included therein. Generally,
the amount of the prodrug used in the treatment methods is that amount
which effectively achieves the desired therapeutic effect in subjects being
treated for a particular disease. Naturally, the dosages of the various
prodrugs encompassed in the compounds of formula (I) will vary
somewhat depending upon the parent drug molecule, rate of in vivo drug
hydrolysis, etc.
The pharmaceutical composition contains about 1 to 99, preferably about
1 to 80 % and most preferably from about 10 to 70% by weight of the
prodrug compound of formula (I) and/or the physiologically tolerable salts
of prodrug compound of formula (I). The effective amount of the active
ingredient of prodrug compound of formula (I) and/or its physiologically
tolerable salts in the pharmaceutical composition in order to obtain a
desired therapeutic effect varies from 1 to 5000 mg. The desirable dosage
of the pharmaceutical composition to be administered can vary over a
wide range. The selected dosage level can be readily determined by a
skilled medical practitioner in the light of the relevant circumstances,
including the condition (diseases or disorder) to be treated, the chosen
route of administration depending on a number of factors, such as age,
weight and physical health and response of the individual patient,
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pharmacokinetics, severity of the disease and the like, factors known in
the medical art. However, in order to obtain desirable effects, it would be
recommended to administer the pharmaceutical composition in the form of
oral tablets (tablets, capsules) daily/weekly/monthly and in a dosage
ranging from 1 mg to 5000 mg, preferably 1 mg to 2000 mg, in a single
dosage form or a multi-dosage form.
The range set forth above is illustrative and those skilled in the art will be
able to determine the optimal dosing of the compounds of formula (I) of the
present invention selected, based on clinical experience and the medical
indication or disease to be treated in a subject in need of the treatment.
Another aspect of the present invention is to provide methods for the
treatment of various medical conditions or diseases or disorders in a
subject comprising administering to a subject in need thereof a
therapeutically effective amount of a compound of formula (I). It has
already been indicated herein above that the compounds of formula (I) of
the present invention are prodrugs of known drugs or therapeutic agents
containing at least one carboxylic acid group. The specific class of
therapeutic agents encompassed within the scope of the invention are
described herein above. According to the present invention, the diseases
or disorders or the medical conditions for the treatment of which the
compounds of formula (I) of the present invention are used are those for
which the parent drug molecule (represented by the variable Dx which
encompasses specific therapeutic agents) is conventionally used by a
medical practitioner.
Moreover, the compounds of formula (I), which are the prodrugs of known
drugs or therapeutic agents, in all likelihood are advantageous over the
parent drug molecules or prodrugs of the parent molecule known hitherto
in the prior art in terms of comparable or potentially superior oral
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=
bioavailability, reduced adverse effect, for instance, gastric irritability
caused by NSAIDS, etc.
It is understood that modifications that do not substantially affect the
activity of the various embodiments of this invention are included within the
scope of the invention disclosed herein. Accordingly, the following
examples are intended to illustrate but not to limit the scope of the present
invention.
Experimental
The abbreviations and terms that are used herein:
(C0C1)2: Oxalyl chloride
DMF: N, N-Dimethylformamide
DCM: Dichloromethane
CBr4: Carbon tetrabromide
TPP: Triphenylphosphine
Et0Ac or EA: Ethyl acetate
.. PE: Petroleum ether
RT: Room Temperature
ACN: Acetonitrile
ZnC12: Zinc Chloride
AgNO3: Silver Nitrate
TEA: Trifluoroacetic acid
HPLC: High Performance Liquid Chromatography
TLC: Thin Layer Chromatography
Example 1:
1-(nitrooxy)ethyl 2-acetoxybenzoate 1-DI-RI
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The title compound was synthesized in 3 steps as shown in Scheme 1 and
the experimental procedure is described below.
Steps 1 and 2: Synthesis of 1-chloroethyl 2-acetoxybenzoate D1-R1-CI
To a stirred suspension of aspirin (40.00 g, 222.22 mmol) in dry DCM (250
mL) were added oxalyl chloride (22.80 mL, 266.56 mmol) and a catalytic
amount of DMF (4-5 drops) at RT under nitrogen. The resulting mixture
was stirred at RT for 3 hours and concentrated to afford aspirin acid
chloride (quantitative) as pale yellow oil. To a stirred solution of the acid
chloride (11.00 g, 55.55 mmol) in dry DCM (100 mL) was added a catalytic
amount of zinc chloride (0.15 g, 1.11 mmol) followed by drop wise addition
of acetaldehyde (3.10 mL, 55.55 mmol) at -15 C under nitrogen. The
reaction mixture was stirred at RT for 16 hours and concentrated. The
residue was dissolved in ethyl acetate (100 mL), washed successively with
water (3 x 100 mL), saturated sodium bicarbonate solution (3 x 100 mL)
and brine (2 x 100 mL), dried over sodium sulfate and concentrated. The
crude compound was purified by silica gel (200-400 mesh) column
chromatography using a gradient of 5 to 15 % ethyl acetate in petroleum
ether as eluent to afford the desired compound D1-R1-CI (3.00 g, .23.0 %)
as colorless oil. 1H NMR (CDCI3, 300 MHz): 6 1.91 (d, J = 5.7 Hz, 3H),
2.39 (s, 3H), 6.75 (q, J = 5.7, 11.7 Hz, 1H), 7.36 (t, J = 7.8 Hz, 1H), 7.60 -
7.64 (m, 1H), 8.00 (dd, J = 1.2, 7.8 Hz, 1H)
Step 3: Synthesis of 1-(nitrooxy)ethyl 2-acetoxybenzoate I-D1-R1
To a stirred solution of 1-chloroethyl 2-acetoxybenzoate D1-R1-CI (3.00 g,
12.29 mmol) in dry acetonitrile (30 mL) was added silver nitrate (3.10 g,
= 18.44 mmol) at RT. The reaction mixture was refluxed at 80 ¨ 90 C for 1
hour, filtered over celite and concentrated. The residue was re-dissolved in
DCM (70 mL); the precipitated silver salt was filtered over celite and the
filtrate was concentrated (this process was repeated twice). The crude
compound was purified by silica gel (200-400 mesh) column
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chromatography using a gradient of 5 to 15 % ethyl acetate in petroleum
ether as eluent to afford 1-DI-RI (2.70 g, 81.0 %) as pale yellow oil. 1H
NMR (CDCI3, 300 MHz): 6 1.66 (d, J = 5.7 Hz, 3H), 2.37 (s, 3H), 7.14 (d, J
= 8.1 Hz, 1H), 7.27 (q, J= 5.4, 11.4 Hz, 1H), 7.33 - 7.36 (m, 1H), 7.60 -
7.64 (m, 1H), 8.0 (dd, J= 1.5, 8.1 Hz, 1H); MS (ES") miz: 268.1 [M-Hr
The compounds of Examples 2 - 8 were synthesized as shown in Scheme
1 by following the experimental procedure for the compound exemplified in
Example 1. The characterization data for the compounds of Examples 2 -
.. 8 is described below:
Example 2:
1-(nitrooxy)propyl 2-acetoxybenzoate I-D1-R2
Steps 1 and 2: Synthesis of 1-chloropropyl 2-acetoxybenzoate D1-R2-CI
The title compound was synthesized using aspirin (5.00 g, 27.78 mmol)
and oxalyl chloride (3.00 rnL, 33.34 mmol) to give aspirin acid chloride which
was reacted with propionaldehyde (1.46 g, 25.23 mmol) in the presence of
.. catalytic amounts of ZnCl2 (0.068 g, 0.50 mmol) to give the corresponding
chloro intermediate D1-R2-CI (1.96 g, 30.0 %) as yellow oil. 1H NMR
(CDCI3, 300 MHz): 6 1.13 (t, J= 7.5 Hz, 3H), 2.09 - 2.20 (m, 2H), 2.39 (s,
3H), 6.60 (t, J = 3.0 Hz, 3H), 7.15 (d, J = 8.1 Hz, 1H), 7.35 (t, J = 7.2 Hz,
1H), 7.60 - 7.63 (m, 1H), 8.06 (dd, J = 1.5, 7.8 Hz, 1H); 13C NMR (CDCI3,
75.47 MHz): 6 9.2, 21.0, 31.6, 76.6, 77.0, 77.4, 85.6, 122.2, 124.1, 126.1,
131.9, 134.7, 151.1, 162.1, 169.6; MS (ES+) m/z 256.3 [M+H]
Step 3: Synthesis of 1-(nitrooxy)propyl 2-acetoxybenzoate I-D1-R2
Nitration of the chloro intermediate D1-R2-CI (1.93 g, 7.52 mmol) with
AgNO3 (1.53 g, 9.02 mmol) afforded the desired nitro compound I-D1-R2
(1.38 g, 65.0 %) as light green oil. 1H NMR (CDCI3, 300 MHz): 6 1.09 (t, J
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= 9.0 Hz, 3H), 1.94 - 2.04 (m, 2H), 2.36 (s, 3H), 7.13 - 7.16 (m, 2H), 7.35
(t, J = 7.2 Hz, 1H), 7.60 - 7.63 (m, 1H), 8.04 (dd, J = 1.5, 7.8 Hz, 1H); 13C
NMR (CDCI3, 75.47 MHz): 6 7.7, 20.9, 24.9, 96.9, 121.7, 124.1, 126.2,
132.0, 134.8, 151.0, 162.2, 169.5; MS (ES+)m/z 358.2 [M+H]
Example 3:
1-(nitrooxy)butyl 2-acetoxybenzoate 1-DI -R3
Steps 1 and 2: Synthesis of 1-chlorobutyl 2-acetoxybenzoate D1-R3-CI
The title compound was synthesized using aspirin (5.00 g, 27.78 mmol)
and oxalyl chloride (3.00 mL, 33.34 mmol) to give aspirin acid chloride.
The aspirin acid chloride was reacted with butyraldehyde (1.81 g, 25.18
, mmol) in the presence of catalytic amounts of ZnCl2 (0.068 g, 0.50 mmol)
to give the corresponding chloro intermediate D1-R3-CI (2.93 g, 43.0 %)
as yellow oil. 1H NMR (CDCI3, 300 MHz): 6 1.00 (t, J = 7.5 Hz, 3H), 1.54 -
1.62 (m, 2H), 2.00 -2.15 (m, 2H), 2.39 (s, 3H), 6.65 (t, J = 6.0 Hz, 1H),
7.15 (d, J- 7.8 Hz, 1H), 7.36 (t, J= 7.5 Hz, 1H), 7.63 (td, J= 7.5, 7.8 Hz,
1H), 8.05 (dd, J = 1.5, 7.8 Hz, 1H); 13C NMR (CDCI3, 75.47 MHz): 6 13.4,
18.2, 21.1, 40.2, 124.1, 126.1, 131.9, 151.1, 162.1, 169.5; MS (ES) m/z
293.0 [M+Na]
Step 3: Synthesis of 1-(nitrooxy)butyl 2-acetoxybenzoate I-DILR3
Nitration of the chloro intermediate D1-R3-CI (2.90 g, 10.71 mmol) with
AgNO3 (2.18 g, 12.85 mmol) afforded the desired nitro compound I-D1-R3
(1.50 g, 47.0 %) as light green oil. 1H NMR (CDCI3, 300 MHz): 6 1.04 (t, J
= 6.0 Hz, 3H), 1.50 - 1.60 (m, 2H), 1.89- 1.97 (m, 2H), 2.36 (s, 3H), 7.20
(t, J = 5.7 Hz, 1H), 7.35 (t, J = 7.8 Hz, 1H), 7.60 - 7.63 (m, 1H), 8.05 (dd,
J
= 1.5, 8.1 Hz, 1H); 130 NMR (CDCI3, 75.47 MHz): 6 13.6, 16.8, 20.9, 33.3,
96.0, 121.8, 124.1, 126.2, 132.0, 134.8, 151.0, 162.2,169.5; MS (ES') m/z
320.0 [M+Na], 336.0 [M+K]
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Example 4:
(2S)-1-(nitrooxy)ethyl 2-(6-methoxynaphthalen-2-yl)propanoate I-02-
R1
Steps 1 and 2: Synthesis of (2S)-1-chloroethyl 2-(6-methoxynaphthalen-2-
yl)propanoate D2-R1-CI
The title compound was synthesized using naproxen (5.00 g, 21.71 mmol)
and oxalyl chloride (5.51 mL, 65.14 mmol) to give naproxen acid chloride
which was reacted with acetaldehyde (1.22 mL, 21.71 mmol) in the
presence of catalytic amounts of ZnCl2 (0.060 g, 0.43 mmol) to give the
corresponding chloro intermediate D2-R1-CI (5.10 g, 80.0 %) as yellow oil.
1H NMR (CDCI3, 300 MHz): 6 1.60 (d, J = 3.0 Hz, 1.5 H), 1.62 (d, J = 3.6
Hz, 1.5 Hz), 1.70 (d, J = 5.7 Hz, 1.5 H), 1.77 (d, J = 5.7 Hz, 1.5 H), 3.89(q,
J= 7.2 Hz, 1H), 3.93 (s, 3H), 6.50 -6.61 (m, 1H), 7.14 -7.18 (m, 2H), 7.37
-7.42 (m, 1H), 7.68 - 7.74 (m, 3H); MS (ES+) m/z 293.1 [M+H]
Step 3: Synthesis of (2S)-1-(nitrooxy)ethyl 2-(6-methoxynaphthalen-2-
yl)propanoate I-D2-R1
Nitration of the chloro intermediate D2-R1-CI (4.00 g, 13.66 mmol) with
AgNO3 (4.64 g, 27.32 mmol) afforded the desired nitro compound I-D2-R1
(3.22 g, 74.0 %) as yellow solid. mp 69 - 71 C; 1H NMR (CDCI3, 300
MHz): 6 1.43 (d, J= 1.5 Hz, 1.5 H), 1.54 (d, J = 1.5 Hz, 1.5 H), 1.58 - 1.59
(m, 3H), 3.88 (q, J = 7.2 Hz, 1H), 3.94(s, 3H), 7.02 -7.09 (m, 1H), 7.14 -
7.19 (m, 2H), 7.36(t, J= 8.9 Hz, 1H), 7.65(d, J = 7.8 Hz, 1H), 7.70 - 7.73
(m, 2H); 130 NMR (CD0I3, 100 MHz): 6 17.6, 18.7, 45.7, 55.7, 81.3, 94.2,
119.5, 126.3, 126.4, 127.7, 129.3, 129.6, 134.2, 134.9, 158.2, 172.8; MS
(ES-) miz 318.1 (M-H), MS (ES+) m/z 320.1 (M+H)+
Example 5:
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(2S)-1-(nitrooxy)propyl 2-(6-methoxynaphthalen-2-yl)propanoate I-D2-
R2
Steps 1 and 2: Synthesis of (2S)-1-chloropropyl 2-(6-methoxynaphthalen-
2-yl)propanoate D2-R2-CI
The title compound was synthesized using naproxen (5.00 g, 21.73 mmol)
and oxalyl chloride (2.20 mL, 26.08 mmol) to give naproxen acid chloride
which was reacted with propionaldehyde (0.74 mL, 10.08 mmol) in the
presence of catalytic amounts of ZnCl2 (0.082 g, 0.60 mmol) to give the
corresponding chloro intermediate D2-R2-CI (0.90 g, 30.0 %) as dark
yellow oil. 1H NMR (CDCI3, 300 MHz): 60.88 - 1.00 (m, 3H), 1.61 (d, J =
6.0 Hz, 3H), 1.99 -2.09 (m, 2H), 3.89 - 3.98 (m, 1H), 3.99 (s, 3H), 6.35 -
6.43 (m, 1H), 7.14 (dd, J = 2.1, 2.4 Hz, 2H), 7.41 (dd, J = 1.5 Hz each,
1H), 7.71 (t, J= 8.3 Hz, 311); MS (ES+) m/z: 307 (M4-H)+
Step 3: Synthesis of (2S)-1-(nitrooxy)propyl 2-(6-methoxynaphthalen-2-
yl)propanoate I-02-R2
Nitration of the chloro intermediate D2-R2-CI (0.90 g, 2.94 mmol) with
AgNO3 (0.59 g, 3.52 mmol) afforded the desired nitro compound I-D2-R2
(0.30 g, 30.7 %) as yellow oil. 1H NMR (CDCI3, 300 MHz): 6 0.83 (t, J = 7.5
Hz, 3H), 1.61 - 1.62 (m, 31-1), 1.80 - 1.90 (m, 2H), 3.86 - 3.91 (m, 1H), 3.93
(s, 3H), 6.90 - 6.94 (m, 1H), 7.13 - 7.18 (m, 2H), 7.34 - 7.36 (m, 1H), 7.65
(d, J = 7.2 Hz, 1H), 7.72 (d, J = 8.7 Hz, 2H); 13C NMR (CDCI3, 75.47 MHz):
6 7.8, 8.0, 18.5, 25.0, 45.7, 55.7, 97.1, 106.1, 119.5, 126.2, 126.4, 127.7,
129.26, 129.6, 134.2, 134.7, 158.1; MS (ES+) miz: 356.1 (M+Na)+
Example 6:
(2S)-1-(nitrooxy)butyl 2-(6-methoxynaphthalen-2-yl)propanoate I-02-
R3
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Steps 1 and 2: Synthesis of (2S)-1-chlorobutyl 2-(6-methoxynaphthalen-2-
yl)propanoate D2-R3-CI
The title compound was synthesized using naproxen (5.00 g, 21.71 mmol)
and oxalyl chloride (5.51 ml_, 65.14 mmol) to give naproxen acid chloride
which was reacted with butyraldehyde (1.94 mL, 21.71 mmol) in the
presence of catalytic amounts of ZnCl2 (0.06 g, 0.43 mmol) to give the
corresponding chloro intermediate D2-R3-CI as yellow oil (4.50 g, 65.0 %);
1H NMR (CDCI3, 300 MHz): 6 0.82 (t, J = 7.3 Hz, 1.5 H), 0.94 (t, J = 7.3
Hz, 1.5 H), 1.26 - 1.33 (m, 1H), 1.42 - 1.50 (m, 1H), 1.59 - 1.63 (m,
3H),1.88 -1.98 (m, 2H), 3.89 (q, J = 7.1 Hz, 1H), 3.93 (s, 3H), 6.40- 6.49
,
(m, 1H), 7.14 - 7.18 (m, 2H), 7.38 - 7.41 (m, 1H), 7.68 - 7.74 (m, 3H).
Step 3: Synthesis of (2S)-1-(nitrooxy)butyl 2-(6-methoxynaphthalen-2-
yl)propanoate I-D2-R3
Nitration of the chloro intermediate D2-R3-CI (2.00 g, 6.23 mmol) with
AgNO3 (2.11 g, 12.46 mmol) afforded the desired nitro compound I-D2-R3
as light yellow oil. Yield: 57.0 %; 1H NMR (CDCI3, 300 MHz): 6 0.84 (t, J =
7.3 Hz, 1.5 H), 0.96 (t, J = 7.3 Hz, 1.5 H), 1.24 -1.47 (m, 2H), 1.59 (d, J=
3.0 Hz, 3H), 1.65 - 1.83 (m, 2H), 3.89 (q, J = 7.2 Hz, 1H), 3.94 (s, 3H),
6.96- 7.00 (m, 1H), 7.14 - 7.19 (m, 2H), 7.36 (t, J = 8.6 Hz, 1H), 7.65 (d, J
= 7.8 Hz, 1H), 7.70 - 7.73 (m, 2H); 1.3,0 NMR (CD0I3, 100 MHz): 6 13.8,
. 25 13.9, 16.9, 17.2, 18.5, 18.6, 33.4, 33.5, 45.6, 45.7, 55.7, 134.2,
134.7,
134.9, 158.1, 173.0; MS (ES+)m/z 360.3 (M+Na)4
Example 7:
(2S)-1-(nitrooxy)pentyl 2-(6-methoxynaphthalen-2-yl)propanoate I-D2-
R4
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Steps 1 and 2: Synthesis of (2S)-1-chloropentyl 2-(6-methoxynaphthalen-
2-yl)propanoate D2-R4-CI
The title compound was synthesized using naproxen (5.00 g, 21.73 mmol)
and oxalyl chloride (2.20 mL, 26.08 mmol) to give naproxen acid chloride
which was reacted with pentanal (0.87 g, 10.05 mmol) in the presence of
catalytic amounts of ZnCl2 (0.082 g, 0.50 mmol) to give the corresponding
chloro intermediate D2-R4-CI (0.80 g, 23.0 %) as dark yellow oil. 1H NMR
(CDCI3, 300 MHz): 5 0.72 -0.94 (m, 3H), 1.18 - 1.19 (m, 2H), 1.25 - 1.41
(m, 2H), 1.61 (d, J = 7.2 Hz, 3H), 1.89 - 2.05 (m, 2H), 3.87 - 3.97 (m, 4H),
6.38 -6.47 (m, 1H), 7.14 - 7.18 (m, 2H), 7.38 - 7.41 (m, 1H), 7.67 - 7.74
(m, 3H); MS (ES) m/z: 335.2 (M+H)+
Step 3: Synthesis of (2S)-1-(nitrooxy)pentyl 2-(6-methoxynaphthalen-2-
yl)propanoate I-02-R4
Nitration of the chloro intermediate D2-R4-CI (0.80 g, 2.39 mmol) with
AgNO3 (0.81 g, 4.70 mmol) afforded the desired nitro compound I-D2-R4
(0.30 g, 34.8 %) as yellow oil. 1H NMR (CDCI3, 300 MHz): 6 0.72 - 0.77
(m, 1H), 0.87- 0.98 (m, 2H), 1.19 - 1.21 (m, 2H), 1.34 - 1.43 (m, 2H),
1.60 - 1.61 (m, 3H), 1.66 - 1.82 (m, 2H), 3.85 - 3.93 (m, 4H), 6.94 -6.99
(m, 1H), 7.13 -7.19 (m, 2H), 7.34 -7.40 (m, 1H), 7.64 - 7.73 (m, 3H); 13C
NMR (CDCI3, 75.47 MHz): 6 13.7, 18.2, 22.0, 25.1, 30.8, 45.4, 55.3, 96.1,
105.6, 119.1, 125.9, 126.1, 127.3, 129.3, 133.8, 134.6, 133.8, 157.8,
172.6; MS (ES+)m/z: 384.11M-1-Nal+
Example 8:
1-(nitrooxy)ethyl 4-(4-(bis(2-chloroethyl)amino)phenyl)butanoate I-D3-
R1
Steps 1 and 2: Synthesis of 1-chloroethyl 4-(4-(bis(2-
chloroethyl)amino)phenyl)butanoate D3-R1-CI
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The title compound was synthesized using chlorambucil (1.00 g, 3.29
mmol) and oxalyl chloride (0.35 mL, 3.95 mmol) to give chlorambucil acid
chloride which was reacted with acetaldehyde (1.50 mL, 26.32 mmol) in
the presence of catalytic amounts of ZnCl2 (0.04 g, 0.33 mmol) to give the
corresponding chloro intermediate 03-R1-CI (0.31 g, 31.0 %) as dark
brown oil. 1H NMR (CDCI3, 300 MHz): 6 1.79 (d, J = 5.7 Hz, 3H), 1.92 -
1.99 (m, 2H), 2.38 (t, J = 7.5 Hz, 2H), 2.59 (t, J = 7.2 Hz, 2H), 3.62 - 3.74
(m, 8H), 6.56 (q, J= 5.7, 1H), 6.64 (d, J = 8.4 Hz, 2H), 7.10 (d, J= 8.4 Hz,
2H)
Step 3: Synthesis of (1-(nitrooxy)ethyl 4-(4-(bis(2-
chloroethyl)amino)phenyl)butanoate I-D3-R1
Nitration of the chloro intermediate D3-RI-Cl (0.10 g, 0.26 mmol) with
AgNO3 (0.050 g, 0.31 mmol) afforded the desired nitro compound I-D3-R1
(0.07 g, 70.0 /0) as brown oil. 1H NMR (CDCI3, 300 MHz): 6 1.55 (d, J =
5.7 Hz, 3H), 1.90 - 1.97 (m, 2H), 2.37 (t, J = 7.2 Hz, 2H), 2.57 (t, J = 7.2
Hz, 2H), 3.62 - 3.74 (m, 8H), 6.65 (d, J = 8.7 Hz, 2H), 7.03 - 7.09 (m, 3H);
MS (ES) m/z: 393 [M+H]
Experimental data - Biological:
Biological Evaluation
The NO-aspirin prodrugs I-D1-R1, I-D1-R2, I-D1-R3 and NO-naproxen
prodrugs I-D2-R1, I-D2-R2, I-D2-R3, I-D2-R4 were evaluated in vivo to
establish their bioavailability and/or anti-inflammatory efficacy. A few
prodrugs with promising bioavailability were selected and evaluated further
for their nitric oxide release capabilities and their gastric ulcer
sparing/inducing effects in comparison to their respective parent drugs.
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The most promising NO-aspirin prodrug I-D1-R1 was further evaluated for
its ability to inhibit thromboxane 82 (TX62) and its efficacy was compared
with that of aspirin at equimolar dose. The prodrugs 1-DI-RI (NO-aspirin)
and I-D2-R1 (NO-naproxen) were also tested for their stability at different
temperatures (RT and 50 C) and in aqueous media (vehicles) such as
aqueous solution of carboxymethyl cellulose (CMC) and polyethylene
glycol (PEG) over a pH range of 1 to 9.
The promising NO-aspirin prodrug I-D1-R1 was further tested for its
stability in Simulated Gastric Fluid (SGF), Simulated Intestinal Fluid (SIF)
and 100% human plasma and its unique capability to release aspirin in
these media thereby acting as a true prodrug of aspirin was determined. It
is well known to the people skilled in the art that it has been a very
difficult
task to design a true ester prodrug of aspirin due to the presence of a very
labile acetyl group which undergoes preferential hydrolysis by plasma
esterases. Consequently, a vast majority of ester prodrugs of aspirin turn
out be prodrugs of salicylic acid.
Pharmacokinetics (PK) of the compounds of invention in rats:
The bioavailability (AUC) data presented for NO-naproxen prodrugs
correspond to the plasma concentration of the released parent drug,
naproxen. However, as mentioned above, the bioavailability data for
aspirin or the NO-aspirin prodrugs correspond to the plasma concentration
of the released salicylic acid rather than that of aspirin due to the fact
that
both aspirin and NO-aspirin prodrugs preferentially undergo de-acetylation
in vivo by plasma esterases to give salicylic acid.
Among the NO-aspirin series, as shown in Figure 1 and Table 7, prodrug I-
D1-R1 showed nearly comparable bioavailability to that of aspirin (AUCs:
91.13 12.20 pg*hr/mL versus 89.78 10.20 pg*hr/mL) and the remaining
two prodrugs not only showed less bioavailability to that of aspirin but also
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exhibited a decreasing trend in bioavailability with increasing length of the
alkyl chain.
In order to assess the species-specific differences in oral bioavailability of
the prodrugs of this invention, we have carried out PK studies on the
promising prodrug I-D1-R1 (NO-aspirin) and aspirin in Wistar rats and the
results are presented in Figure 2 and Table 7.
Interestingly, both aspirin and its prodrug 1-Di-RI have shown comparable
bioavailability (AUCs: 436.8 26.2 pg*hr/mL versus 397.6 28.0
' pg*hr/mL) in Wistar rats also. However, both aspirin and its prodrugs have
shown strikingly improved oral absorption in Wistar rats as compared to
that in Sprague-Dawley (SD) rats (AUCs for Aspirin: 436.8 26.2 versus
91.13 12.20 at 30 mg/kg equimolar dose; AUCs for prodrug I-D1-R1:
397.6 28.0 pg*hr/mL versus 89.78 10.20 pg*hr/mL at 44.83 mg/kg,
which is equimolar to 30 mg/kg dose of aspirin).
Among the NO-naproxen series also, as shown in Figure 3 and Table 7,
the prodrug I-D2-R1 exhibited superior and statistically significant increase
in bioavailability (AUC: 272.60 8.50 pg*hr/mL, **p < 0.01) over that of
naproxen (AUC: 207.80 18.20 pg*hr/mL) in SD rats. It is interesting to
note their important PK parameters. i.e., while Tmax for naproxen was
shown to be < 15 min with a Cmax of about 55 pg/mL, the prodrug I-D2-
R1 showed a Tmax around 1 h with Cmax of about 50 pg/mL. It is also
interesting to note that the plasma drug concentration in prodrug treated
animals was found to be between 30 and 35 pg/mL during the period from
0.5 h to 6.0 h (between 40 and 55 pg/mL during the period between 1 h
and 4 h). However, the plasma drug concentration in naproxen treated
animals, although showed a Cmax of above 55 pg/mL at 15 min, quickly
reached to just above 30 pg/ml in 2 h and to just above 20 pg/mL in a
period of 4 hours and it further dropped to below 15 pg/ml in a period of 8
h. So, the prodrug I-D1-R1 has exhibited controlled release of higher
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amounts of naproxen over a longer period of time (over 30 pg/mL up to 6
= h) when compared to naproxen at equimolar doses. This prodrug is
therefore expected to offer pain relief for a longer period of time than the
parent drug naproxen although the parent drug is expected to offer quicker
relief from pain than its prodrug due to its faster absorption within 15 min
of administration of the drug.
The remaining prodrugs in the naproxen series (i.e., I-D2-R2, I-D2-R3 and
I-D2-R4) exhibited either comparable (I-D2-R2 with an' AUG value of
.. 182.70 8.10 pg*hr/mL) or slightly less (i.e., I-D2-R3 and I-D2-R4 with
AUC values of 178.60 8.10 pg*hr/mL and 177.40 4.10 pg*hr/mL,
respectively) bioavailability when compared to that of naproxen with an
AUC value of 207.80 18.20 pg*hr/mL and also showed some decreasing
trend, although not significant, in bioavailability with increasing chain
length of "Ry" group.
Table 7. Pharmacokinetic study data of compounds of invention:
Plasma Aspirin/Naproxen
Compoundl AUC2' 3'4
(pg*hr/mL)
Aspirin = 91.13 12.20
(436.80 26.20)5
I-D1-R1 89.78 4.90 (397.60
28.00)5
I-D1-R2 73.54 4.90
I-D1-R3 53.56 15.60
Naproxen 207.80 18.20
I-D2-R1 272.60 8.50**
I-D2-R2 182.70 8.10
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I-D2-R3 178.6 8.1
I-D2-R4 177.40 4.1
1,411 the compounds were , administered per oral either at 30mg/kg
equivalent dose of aspirin or 10mg/kg equivalent dose of naproxen.
2Average of pooled samples (n = 3). 3Used SD Rats. 4AUC of aspirin
corresponds to the released plasma salicylate. 5Used Wistar Rats. **p <
0.01 versus Naproxen.
Anti-inflammatory efficacy of representative compounds of the
invention:
It is reported that the anti-inflammatory activity of an NSAID is directly
proportional to the plasma concentration of the drug (Nemmani, K.V.S.,
et al., Bioorganic and Medicinal Chemistry Letters, 2009, 19, 5297-5301
and Pathan, A. R., et al., Inflammopharmacology, 2010, 18, 157-168).
The anti-inflammatory activity of compounds of formula (I) was estimated
based on their respective oral bioavailability data. Moreover, the anti-
inflammatory activity of the compounds of this invention represented by
the formula (I) can be readily assessed in carrageenan-induced rat paw
edema model according to the reported procedure (Al-Swayeh, 0.A., el
al., Br. J. Pharmacol. 2000, 129, 343-350).
Based on its better bioavailability, we expect the prodrug I-D2-R1 (NO-
naproxen) to show superior or at least comparable anti-inflammatory
activity to that of naproxen in the carrageenan-induced rat paw edema
model.
Similarly, based on its nearly comparable bioavailability to aspirin, it is
expected that the prodrug 1-DI-RI (NO-aspirin) would show comparable
anti-inflammatory activity to that of the parent drug aspirin.
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Estimation of nitric oxide release from the compounds of the
invention:
Nitric oxide is reported to act as a mediator of gastrointestinal (GI)
mucosal defense by indirectly suppressing various deleterious events
resulting from NSAID-induced inhibition of COX-1 such as suppression
of prostanoid synthesis, reduction in mucosal blood flow and over-
expression of inflammatory mediators such as plasma tumor necrosis
factor alfa (TNF-a), etc. (Lanas, A. Arthritis Res. Ther. 2008, 10 (Suppl.
2), S4). People with diabetes are believed to be associated with
deficiency of nitric oxide (according to a research report from Florida
University, which can be accessed at www.news.health.ukedu) and may
benefit from the nitric-oxide releasing compounds of this invention. For
example, depleted levels of nitric oxide have been implicated in diseases
such as heart failure, pulmonary hypertension and sexual dysfunction.
.. We therefore evaluated the nitric oxide releasing capability of the
compounds of present invention in rats by taking the two prodrugs 1-Di-
RI (NO-aspirin)= and I-D2-R1 (NO-naproxen) as representative
examples. The nitrate/nitrite release profile in the blood plasma which is
an indirect measure of the nitric oxide released in the blood plasma was
measured using Griess method by employing colorimetric nitrate/nitrite
assay kit from Fluka and the data obtained from the experiment is
presented in Figure 4 and Table 8.
Table 8. Estimation of nitrate / nitrite release from the
compounds of the invention
Plasma Nitrate/Nitrite
Compoundl
AUC (pM*h)
Vehicle 371.10
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I-D1 -R12 1481.00
I-D2-R13 686.80
1A1l the compounds were administered orally; 2N0-aspirin at
a dose equimolar to 10mg/kg dose of aspirin; 3N0-naproxen at a
dose equimolar to 30mg/kg dose of naproxen.
It was observed that significant amounts of nitric oxide (in the form of
nitrite/nitrate) were released from these promising compounds of this
invention represented by formula (I).
Gastric ulcer-sparing properties of compounds of the invention:
The gastric ulcer-sparing potential of prodrugs 1-Di-RI (NO-aspirin at
298.85 mg/kg, which is equimolar to 200 mg/kg dose of aspirin) and I-
02-R1 (NO-naproxen at 138.67 mg/kg, which is equimolar to 100 mg/kg
dose of naproxen) was assessed and compared - with gastric ulcer-
causing potential of their respective parent drugs, aspirin and naproxen
(at doses of 100 mg/kg) in rats. The results (stomach images) from these
experiments are presented in Figures 5A and 6A, respectively. The
results clearly establish that none of the animals treated with prodrugs I-
D1-R1 (NO-aspirin) and I-D2-R1 (NO-naproxen) showed any significant
development of gastric ulcers or lesions. However, severe hemorrhagic
lesions and ulcers were seen to develop in rats administered with parent
drugs, aspirin (100 mg/kg) and naproxen (100 mg/kg). For clarity, the
gastric lesion and ulcer area (in mm2) for aspirin and its prodrug I-D1-R1
(NO-aspirin) is shown in Figure 56. Similarly, the gastric lesion and ulcer
area (in mm2) for naproxen and its prodrug I-D2-R1 (NO-naproxen) is
shown in Figure 6B.
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Inhibition of serum thromboxane B2 (TXB2) formation by Aspirin
and its prodrug
Aspirin is used as an antiplatelet agent for the treatment of
cardiovascular complications. Aspirin shows its antiplatelet activity by
inhibition of platelet cyclooxygenase (COX) (COX is responsible for
generation of a potent platelet activator thromboxane A2 (TXA2)), thus
indirectly inhibiting the formation of serum TXB2 (which is a stable
metabolite of TXA2) (Cox, D., et al., Stroke 2006, 37, 2153-2158). It is
therefore possible to achieve complete suppression of platelet TXA2
.. (and also TXB2) formation via chronic administration of aspirin at a dose
of 30 mg/daily (Patrignani, P., et al. J. Clin, Invest. 1982, 69, 1366-
1372). The antiplatelet activity of aspirin (30 mg/kg) and its prodrug 1-D1-
R1 (at a dose equimolar to 30 mg/kg dose of aspirin) was evaluated in
Sprague-Dawley (SD) rats through estimation of serum TXB2 levels
(Esser, R. et al., Br. J. Pharmacol. 2006, 144, 538-550) and the
experimental results are presented in Figure 7. It was observed that
aspirin (30 mg/kg, p.o., o.d., 7 days) and its prodrug 1-DI-RI (44.82
mg/kg, equivalent to 30 mg/kg of aspirin, p.o., o.d., 7 days) exhibited
nearly comparable inhibition of TXB2 formation (75.97% versus 72.59%)
.. at equimolar doses. The result unequivocally establishes that 1-Di-RI,
which exhibits significant antiplatelet activity (unique to the wonder drug
aspirin), is indeed a true prodrug of aspirin (Figure 7).
Stability of prodrugs 1-D1-R1 (NO-Aspirin) and I-D2-R1 (NO-Naproxen)
at RT and at 50 C:
Stability of prodrugs 1-DI-RI (NO-aspirin) and I-D2-R1 at RT and at 50 C
was tested and the results from the experiments are presented in Table 9.
Table 9. Stability of prodrugs I-D1-R1 and I-D2-R1 at RT and at 50 Ca
I-D1-R1 I-D2-R1
Time RT 50 C RT 50 C
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I-D1- Asp SA I-01- Asp SA I-02- Nap I-D2- Nap
R1 R1 R1 R1
- 0= h 99.14% NIL NIL 99.14% NIL NIL
99.12% NIL 99.12% NIL
2d -- 98.84% NIL 0.1% --
3 d 98.89% NIL NIL --
- 5= d -- 98.18% 0.3% 0.14% --
18 d 98.95% NIL NIL --
25 d -- 98.87% 0.2% 99.00% 0.33%
1 m 98.56% 0.13% NIL 88.34% 2.8% 0.6%
'Samples were kept in capped vials. RT = Room Temperature. Asp = Aspirin. SA =
Salicylic acid.
Nap = Naproxen. d = days. -- = not done. m = month.
Thus, the aspirin prodrug 1-DI-RI was found to be very stable at RT up to
1 month. However, when it was incubated at 50 C, it degraded slightly
(-1%) after 5 days and about 11% after 1 month. After 1 month of
incubation at 50 C, about 2.8% of aspirin and 0.6% of salicylic acid were
generated. In the case of naproxen prodrug I-D2-R1, the prodrug
remained stable both at RT and at 50 C for up to 25 days (period of
study) and released only negligible amounts (-0.20% at RT and -0.33% at
50 C) of naproxen after 25 days.
In-vitro metabolic stability studies on aspirin prodrug in
biologically relevant fluids such as Simulated Gastric Fluid (SGF),
Simulated Intestinal Fluid (SIF) and human plasma:
In order to confirm that the compound I-D1-R1 (NO-aspirin) is indeed
acting as a true prodrug of aspirin, it was incubated in biologically relevant
fluids such as Simulated Gastric Fluid (SGF), Simulated Intestinal Fluid
(SIF) and human plasma and the corresponding results are presented in
Figures 8-11. The prodrug was evaluated at a concentration of either 100
[iM or 1 mM and has shown dose dependent decrease/ increase in the
amount of aspirin released. As shown in the figures, aspirin was co-
evaluated as a positive control under the same experimental conditions, at
equimolar doses, for a meaningful comparison of the results.
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In SGF, as shown in Figure 8, the prodrug 1-DI-RI released significant
amounts (AUC: 10406 M*h) of aspirin, which is only about 15% less than
that of aspirin (AUC: 12348 MTh) at equimolar doses.
In SIF also, as shown in Figure 9, the prodrug 1-DI-RI released significant
amount of aspirin at 1 mM concentration. However, although the aspirin-
release increased in a dose-dependent manner, it was significantly less
(-30%) than that of aspirin standard (AUCs: 136861 mM*h versus 94862
mM*h) at equimolar doses. In SIF, with its pH in the range of ¨6-7, a
certain percentage of the prodrug preferentially underwent de-acetylation
to give salicylic acid derivative which further degraded to salicylic acid.
This aspect of preferential de-acetylation was much more pronounced
when the prodrug I-D1-R1 was incubated in human plasma as shown in
Figure 10.
Thus, in human plasma, the prodrug I-D1-R1 released negligible amount
. (-5%) of aspirin (AUC: 352 1.1.M*h versus 6803 IIM*h for equimolar amount
of aspirin) (Figure 10). However, as expected, a large and proportional
amount of salicylic acid was released, as shown in Figure 11. In this case,
plasma esterases preferentially hydrolyzed 0-acetyl group of the prodrug
to give salicylic acid as the major metabolite.
Although the above examples (prodrugs) were made from NSAIDs, the
technology is not limited but can be extended to other therapeutic agents
containing at least one carboxylic acid group. Thus, we have made one
such example using an anti-cancer drug, chlorambucil, which is
represented by I-D3-R1 (structure shown below).
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cI
I o CH3
NO2
0 0
I-D3-R1
(NO-Chlorambucil)
As anticipated, on incubation in SGF, the prodrug I-D3-R1 also showed
quantitative release of the parent drug, chlorambucil (See Figure 12).
The chlorambucil prodrug I-D3-R1, which is the lowest carbon homologue
in the series, decomposed in SGF to give 100 % of the parent drug
chlorambucil with a half-life of less than 5 minutes.
Example 9:
Pharmacokinetic data for the compounds of the invention
Representative compounds of formula (I) of the present invention that
are the nitric oxide releasing prodrugs of known drugs or therapeutic
agents containing at least one carboxylic acid group, were subjected to
pharmacokinetic study and the method and results of the study are
presented herein below:
Animals:
Male Sprague-Dawley (SD) rats weighing 150-220 g were used in the
study (Exception: Wistar rats were used for one study). The rats were
fed normal standard laboratory chow and maintained under standard
environmental conditions (room temperature of 22 2 C; 50 10 %
relative humidity; 12 hrs light-dark cycle). All experimental procedures
mentioned below were approved by the institutional animal ethics
committee and were performed in accordance with standard guidelines
of Committee for the purpose of control and supervision of experiments
on animals (CPCSEA); Govt. of India for the experiment on animals.
General Procedures:
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The oral pharmacokinetic profile of the compounds of the invention was
studied in male Sprague-Dawley (SD) rats. However, for one study,
Wistar rats were used. For the purpose of these studies, the nitric oxide
releasing prodrugs of drugs containing a carboxylic acid functional
group, e.g. naproxen and aspirin, which are encompassed in the
compounds of formula (I), were selected as representative examples.
The release profiles of parent drugs, naproxen and aspirin from their
nitric oxide releasing prodrugs were analyzed by a HPLC system.
HPLC Sample preparation and standard curve:
HPLC: Waters Alliance analytical HPLC equipped with 2996 PDA
detector and Empower software were used to analyze the
samples.
HPLC Column: Waters X-Terra RP-18 reversed phase column, 150 x
3.9 mm, 5 M
HPLC Method: Flow: 1 mUmin, detector set at 210 nm and at Maxplot
(210-400 nm range);
Solvent A: Acetonitrile;
Solvent B: 0.1% TFA in water.
Injection volume: 20 tI
Elution method: A linear gradient as specified below:
Time in min 0-2 2-10 10-13 13-14 14-18
%A 20 20-100 100 100-20 20
Blood samples were collected from the rats and the plasma was
separated by centrifugation at 1000xg for 5 min at 4 C. A stock solution
of the parent drug was prepared by dissolving it in acetonitrile and
working solutions of various concentrations (0.625, 1.25, 2.5, 5, 10, 20
pg/mL) were prepared by spiking the blood plasma with the naproxen
stock solution. Each plasma sample (50 I) was then transferred to a
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micro centrifuge tube containing acetonitrile (200 I), mixed by vortex
and centrifuged for 5 min (1000xg) at 4 C. The supernatant layer (150
I) obtained after centrifugation was then transferred to HPLC vials. The
sample solution (25 pi) was then injected in to HPLC for analysis. A
linear calibration curve between the naproxen concentration in plasma
(0.625, 1.25, 2.5, 5, 10, 20 g/mL) and the peak area ratio was obtained.
The rats were divided into groups and three rats were placed in each
group. Parent NSAID (i.e., aspirin at a dose of 30 mg/kg or naproxen at a
dose of 10 mg/kg) was administered orally to one group of rats and the
representative compounds of formula (I), i.e., the nitric oxide releasing
prodrugs of aspirin (i.e., 1-DI-RI, I-D1-R2 and I-D1-R3, at a dose
equivalent to 30 mg/kg of aspirin) and naproxen (i.e., 1-02-R1, I-D2-R2,
02-R3 and I-D2-R4, at a dose equivalent to 10 mg/kg of naproxen) were
administered orally to the remaining groups. Blood was collected from
orbital plexus of the rats according to a specific schedule (0.25, 0.5, 1, 2,
4, 6 and 8 h after dosing) and the plasma was separated from each
sample by centrifugation for 5 min (1000xg) at 4 C. Each collected
plasma sample (50 I) corresponding to respective parent drug (i.e.,
aspirin or naproxen) and the aforementioned nitric oxide releasing
prodrugs of aspirin or naproxen was then transferred to a micro
centrifuge tube containing acetonitrile (200 pi), mixed by vortex and
centrifuged for 5 min (1000xg) at 4 C. The supernatant layer (150 I)
obtained after centrifugation was then transferred to HPLC vials. A (25
I) volume of each sample solution was injected into HPLC for analysis.
.. The plasma concentration of salicylic acid or naproxen in rats after oral
administration of the respective parent drugs (i.e., aspirin or naproxen)
and their respective nitric oxide releasing prodrugs versus time intervals
was plotted and the area under the curve was determined by trapezoidal
rule (Gibaldi, M. and Perrier, D., Pharmacokinetics, Second edition,
.. 15:445-447) for each of the samples corresponding to parent drug
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(aspirin or naproxen) and their respective nitric oxide releasing prodrugs.
The AUC values for the nitric oxide releasing prodrugs of aspirin and
naproxen were determined.
Example 10:
Estimation of nitrate / nitrite release from the compounds of the
invention in-vivo:
Male Sprague-Dawley (SD) rats (180-220 g) were acclimatized for a
week and fasted 12-14 hours prior to the commencement of the
experiment. The representative compounds of formula (I), i.e., the nitric
oxide releasing prodrugs of aspirin (i.e., I-D1-R1) at a dose equivalent to
30 mg/kg dose of aspirin and naproxen (I-D2-R1) at a dose equivalent to
10 mg/kg dose of naproxen were administered orally to the rats. The
blood sample was collected from the rats administered with each of the
aforementioned nitric oxide releasing prodrugs of aspirin and naproxen
according to a specific schedule (0.5, 1, 2, 4, 6 and 8 hours) and the
plasma was separated by centrifugation (1000xg) for 5 min at 4 C. The
release profile of the nitrate/nitrite in the blood plasma which is an
indirect measure of the nitric oxide released in the blood plasma was
measured using Griess method by employing colorimetric nitrate/nitrite
assay kit from Fluka.
The blood plasma samples were filtered using Millipore ultra-filtration 96-
well plate to remove the plasma proteins having particle size of >10 kDa.
The assay was performed in a 96-well plate according to standard
procedure described in the kit. The method comprised adding to the well,
standard (sodium nitrate) (80 I) of various concentrations (0, 20, 40, 60,
80 and 100 11M) followed by the reagents, nitrate reductase (10 }.1,1) and
enzyme co-factor (10 )_11). The plasma sample (80 I) obtained from the
blood sample collected at various time intervals from the rats (0.5, 1, 2,
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4, 6 and 8 hours) were added to separate wells, followed by the
reagents, nitrate reductase (10 111) and enzyme co-factor (10 pi). The
plate was incubated for 2 h at room temperature on orbital shaker (350-
400 rpm). Griess reagent A (50 pi) was added to each well followed by
incubation for 5 min and subsequently, Griess reagent B (50 ktl) was
added to each well followed by incubation for 10 min. The absorbance of
assay plate was measured by using a 96-well plate reader (Bio-Tek
instruments) at 540 nm. This procedure was carried out for each of the
aforementioned nitric oxide releasing prodrugs of aspirin and naproxen
individually. A standard curve between the sodium nitrate concentration
(.1M) (0, 20, 40, 60, 80 and 100 M) on X-axis versus absorbance values
on Y-axis was plotted. The absorbance values of each of the plasma
samples collected at different time intervals corresponding to the
aforementioned nitric oxide releasing prodrugs of aspirin and naproxen
from the rats was compared with the standard curve to determine the
plasma nitrate concentration in mice after oral administration of the
aforementioned nitric oxide releasing prodrugs of aspirin and naproxen.
The plasma nitrate concentration in rats after oral administration of the
aforementioned nitric oxide releasing prodrugs of aspirin and naproxen
versus time intervals was plotted and the area under the curve was
determined for each of the samples corresponding to the aforementioned
nitric oxide releasing prodrugs of aspirin and naproxen (Figure 4).
Example 11:
Determination of the anti-inflammatory activity of the compounds of
the invention
With an intention to save resources and experimental animals, anti-
inflammatory activity of the compounds of this invention was not
determined experimentally. The decision was based on the observation
= 30 that the anti-inflammatory activity of a drug is generally shown
to be
directly proportional to the amount of drug present in the blood plasma.
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Since the AUC values (i.e., bioavailability) of some representative
compounds of this invention are comparable [in case of aspirin prodrug I-
D1-R1 (NO-aspirin)] or superior [in case of naproxen prodrug I-D2-R1
(NO-naproxen)] to those of their respective parent drugs aspirin or
naproxen, we have intentionally not tested anti-inflammatory activity of
these promising NO-NSAIDs. However, the anti-inflammatory activity of
NO-aspirin (i.e., I-D1-R1) and NO-naproxen (i.e., I-D2-R1) and their
respective parent drugs aspirin and naproxen can be assessed in
carrageenan-induced rat paw edema model according to the reported
procedure (0.A. Al-Swayeh, 0. A., et al., Br. J. Pharmacol. 2000, 129,
343-350). Thus, Male Sprague-Dawley (SD) rats are to be divided into
three groups consisting of ten rats in each group. Parent drugs aspirin
(30 mg/kg) or naproxen (10 mg/kg) and NO-aspirin (I-D1-R1, at a dose
equivalent to 30 mg/kg dose of aspirin) and NO-naproxen (I-D2-R1, at a
dose equivalent to 10 mg/kg dose of naproxen) are to be dissolved in
PEG 400 and administered orally to overnight fasted rats of different
groups. One hour later, carrageenan (100 pi, 1% w/v) is to be injected in
to their paws. The control group is to be given PEG 400 (1mL/kg). The
paw volume of the groups of rats administered with parent drugs and
those administered with prodrugs are to be measured before
carrageenan injection and also at a time period of 3 and 5 hours after the
injection of carrageenan. The (%) inhibition of paw edema in rats
administered with parent drugs (aspirin and naproxen) and NO-NSAIDS
(I-D1-R1 and I-D2-R1) after 3 and 5 hours, respectively, are to be
calculated and compared with that of the control group.
Example 12:
Acute Gastric Ulcerogenesis activity study:
The ulcerogenic potential of NO-aspirin (i.e., I-D1-R1) and NO-naproxen
(i.e., I-D2-R1) was assessed in rats. Thus, aspirin (100 mg/kg) and
naproxen (100 mg/kg) and their respective nitric oxide releasing
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prodrugs I-01-R1 and I-02-R1 (at doses equivalent to 100 mg/kg of
aspirin and naproxen, respectively) were administered to overnight
fasted rats of different groups. The animals were sacrificed after 5 h of
drug administration. The stomachs of the treated animals were
separated, perfused with 2 % formalin (10 mL), and a large curvature
was excised. The severity of the mucosal damage was assessed on the
basis of the size of the observed ulcer lesions in the images captured
using a stereomicroscope attached to a digital camera (Stemi 2000,
Zeiss, Germany). The Image Pro Plus software (version 5.1) was used to
quantify the hemorrhagic/ulcer lesions in pixels and to convert them into
mm2. The total area of lesions was calculated for each treatment group
and the measure of gastric ulcers (Mean SEM) (mm2) was estimated
(Figures 5 and 6).
Example 13:
Estimation of serum TXB2 levels:
In vivo TXB2 inhibition potential of aspirin and NO-aspirin prodrugs was
assessed in Sprague-Dawley (SD) rats; the serum TXB2 levels were
estimated according to the reported procedure (R. Esser, R., et al., Br. J.
Pharmacol. 2006, 144, 538-550). Thus, vehicle, aspirin (30 mg/kg) or
aspirin prodrug I-D1-R1 (44.82 mg/kg which is equivalent to 30 mg/kg
dose of aspirin) were administered orally to the overnight fasted SD rats.
After six hours of drug administration, the blood samples were obtained
from the rats by retro-orbital plexus puncture under light isoflurane
anesthesia. The whole blood samples were immediately transferred into
glass tubes and allowed to clot at 37 C for 60 min; the serum was
separated by centrifugation (10 min at 2000 rpm) and kept at -20 C until
assayed for TXB2. The serum TXB2 concentrations were determined by
enzyme immunoassay (EIA) using commercially available TXB2 estimation
kit (Cayman Chemicals, USA), according to the method described in kit
information booklet.
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Example 14:
In-vitro metabolic stability studies in biological fluids
Preparation of Biological fluids
Simulated Gastric Fluid (SGF): SGF was prepared according to the
procedure described in Test Solution - USP. Thus, 0.2 g of sodium
chloride and 0.32 g of purified pepsin (Sigma, derived from porcine
stomach mucosa with an activity of 800 to 2500 units per mg of protein)
were dissolved in 0.7 mL of hydrochloric acid and sufficient water to make
100 mL. This test solution has a pH of about 1.2 and was utilized for in-
vitro studies.
Simulated Intestinal Fluid (SIF): SIF was prepared according to the
procedure described in Test Solution - USP. Thus, 0.68 g of monobasic
potassium phosphate was dissolved in 25 mL of water followed by addition
of 0.2N NaOH (7.7 mL) and water (50 mL). To this solution was added
pancreatin (1 g) and mixed; the pH of the resulting solution was adjusted
to about 6.8 with 0.2N HCl/ 0.2N NaOH and the solution was diluted with
water to 100 mL. The solution was utilized for in-vitro studies.
Human Plasma: Human plasma was similarly obtained by processing the
blood taken from healthy human male volunteers (age group 25-35 years)
who had not consumed any NSAIDS one week prior to the collection of
blood. This plasma was utilized for the in-vitro experiments.
In-vitro metabolic stability of aspirin, naproxen and their respective
prodrugs (NO-
aspirin) and I-D2-R1 (NO-naproxen) in
Simulated Gastric Fluid (SGF), Simulated Intestinal Fluid (SIF) and
Human Plasma:
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The solution of the test compound in acetonitrile (10 pL of 100 pM
solution) was dissolved in 990 pL of biological fluid (SGF/SIF/Human
Plasma). The resulting reaction mixtures were incubated at 37 C. At
specified time intervals, aliquots (60 pL) were withdrawn and added to
acetonitrile (200 pL) and mixed well by vortexing for 2 minutes. The
mixture was centrifuged at 13000 rpm for 15 min at 4 C, and the
supernatant analyzed by HPLC. The amounts (area percentages) of the
remaining intact prodrug (if any) and the released metabolite(s) were
estimated by HPLC.
Statistical Analysis
Statistical analyses of data consisting of three or more groups were
performed using one-way analysis of variance (one-way ANOVA) followed
by post-hoc Dunnett's multiple comparison test, and values of p<0.05 were
considered as significant. For data consisting of two groups, analyses
were performed using student's t test and values of p<0.05 were
considered as significant. All analyses were carried out using GraphPad
Prism version 4.00 for Windows (GraphPad Software, San Diego, CA,
= USA). For data consisting of only pooled/mean values, the statistical
analysis could not be performed.
HPLC Analysis
This was performed by using HPLC instrument (Waters alliance), pump
2695, and PDA detector 2996 with the following chromatographic
parameters: Wavelength -210 nm; Column - Waters X-Terra RP-18, 150 x
3.9 mm, 5 pm; Injection volume, 25 pL; Run time, 13 min. Mode of
operation was linear gradient with mobile phase A: Acetonitrile and B: 0.1
% TFA in water (filtered and degassed). Flow rate was 1.0 mL/min at 25
C.
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